diff --git a/httprunner/built_in.py b/httprunner/built_in.py
deleted file mode 100644
index 43524d3f..00000000
--- a/httprunner/built_in.py
+++ /dev/null
@@ -1,206 +0,0 @@
-# encoding: utf-8
-
-"""
-Built-in dependent functions used in YAML/JSON testcases.
-"""
-
-import datetime
-import os
-import random
-import re
-import string
-import time
-
-import filetype
-from requests_toolbelt import MultipartEncoder
-
-from httprunner.compat import basestring, builtin_str, integer_types
-from httprunner.exceptions import ParamsError
-
-PWD = os.getcwd()
-
-
-###############################################################################
-##  built-in functions
-###############################################################################
-
-def gen_random_string(str_len):
-    """ generate random string with specified length
-    """
-    return ''.join(
-        random.choice(string.ascii_letters + string.digits) for _ in range(str_len))
-
-
-def get_timestamp(str_len=13):
-    """ get timestamp string, length can only between 0 and 16
-    """
-    if isinstance(str_len, integer_types) and 0 < str_len < 17:
-        return builtin_str(time.time()).replace(".", "")[:str_len]
-
-    raise ParamsError("timestamp length can only between 0 and 16.")
-
-
-def get_current_date(fmt="%Y-%m-%d"):
-    """ get current date, default format is %Y-%m-%d
-    """
-    return datetime.datetime.now().strftime(fmt)
-
-
-def sleep(n_secs):
-    """ sleep n seconds
-    """
-    time.sleep(n_secs)
-
-
-###############################################################################
-##  upload files with requests-toolbelt
-#   e.g.
-#   - test:
-#      name: upload file
-#      variables:
-#          file_path: "data/test.env"
-#          multipart_encoder: ${multipart_encoder(file=$file_path)}
-#      request:
-#          url: /post
-#          method: POST
-#          headers:
-#              Content-Type: ${multipart_content_type($multipart_encoder)}
-#          data: $multipart_encoder
-#      validate:
-#          - eq: ["status_code", 200]
-#          - startswith: ["content.files.file", "UserName=test"]
-###############################################################################
-
-def multipart_encoder(**kwargs):
-    """ initialize MultipartEncoder with uploading fields.
-    """
-
-    def get_filetype(file_path):
-        file_type = filetype.guess(file_path)
-        if file_type:
-            return file_type.mime
-        else:
-            return "text/html"
-
-    fields_dict = {}
-    for key, value in kwargs.items():
-
-        if os.path.isabs(value):
-            _file_path = value
-            is_file = True
-        else:
-            global PWD
-            _file_path = os.path.join(PWD, value)
-            is_file = os.path.isfile(_file_path)
-
-        if is_file:
-            filename = os.path.basename(_file_path)
-            with open(_file_path, 'rb') as f:
-                mime_type = get_filetype(_file_path)
-                fields_dict[key] = (filename, f.read(), mime_type)
-        else:
-            fields_dict[key] = value
-
-    return MultipartEncoder(fields=fields_dict)
-
-
-def multipart_content_type(multipart_encoder):
-    """ prepare Content-Type for request headers
-    """
-    return multipart_encoder.content_type
-
-
-###############################################################################
-##  built-in comparators
-###############################################################################
-
-def equals(check_value, expect_value):
-    assert check_value == expect_value
-
-
-def less_than(check_value, expect_value):
-    assert check_value < expect_value
-
-
-def less_than_or_equals(check_value, expect_value):
-    assert check_value <= expect_value
-
-
-def greater_than(check_value, expect_value):
-    assert check_value > expect_value
-
-
-def greater_than_or_equals(check_value, expect_value):
-    assert check_value >= expect_value
-
-
-def not_equals(check_value, expect_value):
-    assert check_value != expect_value
-
-
-def string_equals(check_value, expect_value):
-    assert builtin_str(check_value) == builtin_str(expect_value)
-
-
-def length_equals(check_value, expect_value):
-    assert isinstance(expect_value, integer_types)
-    assert len(check_value) == expect_value
-
-
-def length_greater_than(check_value, expect_value):
-    assert isinstance(expect_value, integer_types)
-    assert len(check_value) > expect_value
-
-
-def length_greater_than_or_equals(check_value, expect_value):
-    assert isinstance(expect_value, integer_types)
-    assert len(check_value) >= expect_value
-
-
-def length_less_than(check_value, expect_value):
-    assert isinstance(expect_value, integer_types)
-    assert len(check_value) < expect_value
-
-
-def length_less_than_or_equals(check_value, expect_value):
-    assert isinstance(expect_value, integer_types)
-    assert len(check_value) <= expect_value
-
-
-def contains(check_value, expect_value):
-    assert isinstance(check_value, (list, tuple, dict, basestring))
-    assert expect_value in check_value
-
-
-def contained_by(check_value, expect_value):
-    assert isinstance(expect_value, (list, tuple, dict, basestring))
-    assert check_value in expect_value
-
-
-def type_match(check_value, expect_value):
-    def get_type(name):
-        if isinstance(name, type):
-            return name
-        elif isinstance(name, basestring):
-            try:
-                return __builtins__[name]
-            except KeyError:
-                raise ValueError(name)
-        else:
-            raise ValueError(name)
-
-    assert isinstance(check_value, get_type(expect_value))
-
-
-def regex_match(check_value, expect_value):
-    assert isinstance(expect_value, basestring)
-    assert isinstance(check_value, basestring)
-    assert re.match(expect_value, check_value)
-
-
-def startswith(check_value, expect_value):
-    assert builtin_str(check_value).startswith(builtin_str(expect_value))
-
-
-def endswith(check_value, expect_value):
-    assert builtin_str(check_value).endswith(builtin_str(expect_value))
diff --git a/httprunner/builtin/__init__.py b/httprunner/builtin/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/httprunner/builtin/comparators.py b/httprunner/builtin/comparators.py
new file mode 100644
index 00000000..3a522993
--- /dev/null
+++ b/httprunner/builtin/comparators.py
@@ -0,0 +1,99 @@
+"""
+Built-in validate comparators.
+"""
+
+import re
+
+from httprunner.compat import basestring, builtin_str, integer_types
+
+
+def equals(check_value, expect_value):
+    assert check_value == expect_value
+
+
+def less_than(check_value, expect_value):
+    assert check_value < expect_value
+
+
+def less_than_or_equals(check_value, expect_value):
+    assert check_value <= expect_value
+
+
+def greater_than(check_value, expect_value):
+    assert check_value > expect_value
+
+
+def greater_than_or_equals(check_value, expect_value):
+    assert check_value >= expect_value
+
+
+def not_equals(check_value, expect_value):
+    assert check_value != expect_value
+
+
+def string_equals(check_value, expect_value):
+    assert builtin_str(check_value) == builtin_str(expect_value)
+
+
+def length_equals(check_value, expect_value):
+    assert isinstance(expect_value, integer_types)
+    assert len(check_value) == expect_value
+
+
+def length_greater_than(check_value, expect_value):
+    assert isinstance(expect_value, integer_types)
+    assert len(check_value) > expect_value
+
+
+def length_greater_than_or_equals(check_value, expect_value):
+    assert isinstance(expect_value, integer_types)
+    assert len(check_value) >= expect_value
+
+
+def length_less_than(check_value, expect_value):
+    assert isinstance(expect_value, integer_types)
+    assert len(check_value) < expect_value
+
+
+def length_less_than_or_equals(check_value, expect_value):
+    assert isinstance(expect_value, integer_types)
+    assert len(check_value) <= expect_value
+
+
+def contains(check_value, expect_value):
+    assert isinstance(check_value, (list, tuple, dict, basestring))
+    assert expect_value in check_value
+
+
+def contained_by(check_value, expect_value):
+    assert isinstance(expect_value, (list, tuple, dict, basestring))
+    assert check_value in expect_value
+
+
+def type_match(check_value, expect_value):
+    def get_type(name):
+        if isinstance(name, type):
+            return name
+        elif isinstance(name, basestring):
+            try:
+                return __builtins__[name]
+            except KeyError:
+                raise ValueError(name)
+        else:
+            raise ValueError(name)
+
+    assert isinstance(check_value, get_type(expect_value))
+
+
+def regex_match(check_value, expect_value):
+    assert isinstance(expect_value, basestring)
+    assert isinstance(check_value, basestring)
+    assert re.match(expect_value, check_value)
+
+
+def startswith(check_value, expect_value):
+    assert builtin_str(check_value).startswith(builtin_str(expect_value))
+
+
+def endswith(check_value, expect_value):
+    assert builtin_str(check_value).endswith(builtin_str(expect_value))
diff --git a/httprunner/builtin/functions.py b/httprunner/builtin/functions.py
new file mode 100644
index 00000000..0cca0295
--- /dev/null
+++ b/httprunner/builtin/functions.py
@@ -0,0 +1,105 @@
+"""
+Built-in functions used in YAML/JSON testcases.
+"""
+
+import datetime
+import os
+import random
+import string
+import time
+
+import filetype
+from requests_toolbelt import MultipartEncoder
+
+from httprunner.compat import builtin_str, integer_types
+from httprunner.exceptions import ParamsError
+
+PWD = os.getcwd()
+
+
+def gen_random_string(str_len):
+    """ generate random string with specified length
+    """
+    return ''.join(
+        random.choice(string.ascii_letters + string.digits) for _ in range(str_len))
+
+
+def get_timestamp(str_len=13):
+    """ get timestamp string, length can only between 0 and 16
+    """
+    if isinstance(str_len, integer_types) and 0 < str_len < 17:
+        return builtin_str(time.time()).replace(".", "")[:str_len]
+
+    raise ParamsError("timestamp length can only between 0 and 16.")
+
+
+def get_current_date(fmt="%Y-%m-%d"):
+    """ get current date, default format is %Y-%m-%d
+    """
+    return datetime.datetime.now().strftime(fmt)
+
+
+def sleep(n_secs):
+    """ sleep n seconds
+    """
+    time.sleep(n_secs)
+
+
+"""
+upload files with requests-toolbelt
+e.g.
+
+    - test:
+        name: upload file
+        variables:
+            file_path: "data/test.env"
+            multipart_encoder: ${multipart_encoder(file=$file_path)}
+        request:
+            url: /post
+            method: POST
+            headers:
+                Content-Type: ${multipart_content_type($multipart_encoder)}
+            data: $multipart_encoder
+        validate:
+            - eq: ["status_code", 200]
+            - startswith: ["content.files.file", "UserName=test"]
+"""
+
+
+def multipart_encoder(**kwargs):
+    """ initialize MultipartEncoder with uploading fields.
+    """
+
+    def get_filetype(file_path):
+        file_type = filetype.guess(file_path)
+        if file_type:
+            return file_type.mime
+        else:
+            return "text/html"
+
+    fields_dict = {}
+    for key, value in kwargs.items():
+
+        if os.path.isabs(value):
+            _file_path = value
+            is_file = True
+        else:
+            global PWD
+            _file_path = os.path.join(PWD, value)
+            is_file = os.path.isfile(_file_path)
+
+        if is_file:
+            filename = os.path.basename(_file_path)
+            with open(_file_path, 'rb') as f:
+                mime_type = get_filetype(_file_path)
+                fields_dict[key] = (filename, f.read(), mime_type)
+        else:
+            fields_dict[key] = value
+
+    return MultipartEncoder(fields=fields_dict)
+
+
+def multipart_content_type(multipart_encoder):
+    """ prepare Content-Type for request headers
+    """
+    return multipart_encoder.content_type
diff --git a/httprunner/loader/buildup.py b/httprunner/loader/buildup.py
index 14c7b3bd..b2e9a16d 100644
--- a/httprunner/loader/buildup.py
+++ b/httprunner/loader/buildup.py
@@ -1,7 +1,8 @@
 import importlib
 import os
 
-from httprunner import built_in, exceptions, logger, utils
+from httprunner import exceptions, logger, utils
+from httprunner.builtin import functions
 from httprunner.loader.load import load_module_functions, load_folder_content, load_file, load_dot_env_file, \
     load_folder_files
 from httprunner.loader.locate import init_project_working_directory, get_project_working_directory
@@ -481,7 +482,7 @@ def load_project_data(test_path, dot_env_path=None):
     # locate PWD and load debugtalk.py functions
 
     project_mapping["PWD"] = project_working_directory
-    built_in.PWD = project_working_directory
+    functions.PWD = project_working_directory   # TODO: remove
     project_mapping["functions"] = debugtalk_functions
     project_mapping["test_path"] = test_path
 
diff --git a/httprunner/loader/load.py b/httprunner/loader/load.py
index 5b511926..0e89580f 100644
--- a/httprunner/loader/load.py
+++ b/httprunner/loader/load.py
@@ -5,7 +5,7 @@ import os
 
 import yaml
 
-from httprunner import built_in
+from httprunner.builtin import functions
 from httprunner import exceptions, logger, utils
 from httprunner.loader.check import check_testcase_format, is_function
 from httprunner.loader.locate import get_project_working_directory
@@ -235,7 +235,7 @@ def load_module_functions(module):
 
 
 def load_builtin_functions():
-    """ load built_in module functions
+    """ load builtin module functions
     """
-    return load_module_functions(built_in)
+    return load_module_functions(functions)
 
diff --git a/tests/api_server.py b/tests/api_server.py
index d3a370d4..c7c73eee 100644
--- a/tests/api_server.py
+++ b/tests/api_server.py
@@ -5,7 +5,7 @@ from functools import wraps
 
 from flask import Flask, make_response, request
 
-from httprunner.built_in import gen_random_string
+from httprunner.builtin.functions import gen_random_string
 
 try:
     from httpbin import app as httpbin_app
diff --git a/tests/test_response.py b/tests/test_response.py
index 8dade20b..ddd90d54 100644
--- a/tests/test_response.py
+++ b/tests/test_response.py
@@ -1,6 +1,6 @@
 import requests
 
-from httprunner import built_in, exceptions, loader, response
+from httprunner import exceptions, response
 from httprunner.compat import basestring, bytes
 from tests.api_server import HTTPBIN_SERVER
 from tests.base import ApiServerUnittest
@@ -8,9 +8,6 @@ from tests.base import ApiServerUnittest
 
 class TestResponse(ApiServerUnittest):
 
-    def setUp(self):
-        self.functions_mapping = loader.load.load_module_functions(built_in)
-
     def test_parse_response_object_json(self):
         url = "http://127.0.0.1:5000/api/users"
         resp = requests.get(url)
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 6afd7dc5..c61eaabe 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -62,8 +62,8 @@ class TestUtils(ApiServerUnittest):
         self.assertEqual(result, "L")
 
     def current_validators(self):
-        from httprunner import built_in
-        functions_mapping = loader.load.load_module_functions(built_in)
+        from httprunner.builtin import comparators
+        functions_mapping = loader.load.load_module_functions(comparators)
 
         functions_mapping["equals"](None, None)
         functions_mapping["equals"](1, 1)