diff --git a/README.md b/README.md
index 845490a9..e8911f39 100644
--- a/README.md
+++ b/README.md
@@ -82,6 +82,7 @@ func TestCaseDemo(t *testing.T) {
                 AssertEqual("body.json.foo2", 12.3, "check args foo2"),
             hrp.Step("post form data").
                 POST("/post").
+                WithHeaders(map[string]string{"Content-Type": "application/x-www-form-urlencoded; charset=UTF-8"}).
                 WithParams(map[string]interface{}{
                     "foo1": "$varFoo1",       // reference former extracted variable
                     "foo2": "${max($a, $b)}", // 12.3; step level variables are independent, variable b is 3.45 here
diff --git a/convert_test.go b/convert_test.go
index b772b746..b03cc7b4 100644
--- a/convert_test.go
+++ b/convert_test.go
@@ -49,7 +49,8 @@ var demoTestCase = &TestCase{
 			AssertEqual("body.json.foo2", 12.3, "check args foo2"),
 		Step("post form data").
 			POST("/post").
-			WithParams(map[string]interface{}{
+			WithHeaders(map[string]string{"Content-Type": "application/x-www-form-urlencoded; charset=UTF-8"}).
+			WithBody(map[string]interface{}{
 				"foo1": "$varFoo1",       // reference former extracted variable
 				"foo2": "${max($a, $b)}", // 12.3; step level variables are independent, variable b is 3.45 here
 			}).
diff --git a/examples/demo.json b/examples/demo.json
index 855a73dd..4f371a05 100644
--- a/examples/demo.json
+++ b/examples/demo.json
@@ -100,7 +100,10 @@
             "request": {
                 "method": "POST",
                 "url": "/post",
-                "params": {
+                "headers": {
+                    "Content-Type": "application/x-www-form-urlencoded; charset=UTF-8"
+                },
+                "body": {
                     "foo1": "$varFoo1",
                     "foo2": "${max($a, $b)}"
                 }
diff --git a/examples/demo.yaml b/examples/demo.yaml
index 35eec3c8..0bc18920 100644
--- a/examples/demo.yaml
+++ b/examples/demo.yaml
@@ -67,7 +67,9 @@ teststeps:
       request:
         method: POST
         url: /post
-        params:
+        headers:
+            Content-Type: application/x-www-form-urlencoded; charset=UTF-8
+        body:
             foo1: $varFoo1
             foo2: ${max($a, $b)}
       validate:
diff --git a/examples/demo_test.go b/examples/demo_test.go
index 301abf80..f7c19e82 100644
--- a/examples/demo_test.go
+++ b/examples/demo_test.go
@@ -49,6 +49,7 @@ func TestCaseDemo(t *testing.T) {
 				AssertEqual("body.json.foo2", 12.3, "check args foo2"),
 			hrp.Step("post form data").
 				POST("/post").
+				WithHeaders(map[string]string{"Content-Type": "application/x-www-form-urlencoded; charset=UTF-8"}).
 				WithParams(map[string]interface{}{
 					"foo1": "$varFoo1",       // reference former extracted variable
 					"foo2": "${max($a, $b)}", // 12.3; step level variables are independent, variable b is 3.45 here
diff --git a/runner.go b/runner.go
index cebf0392..d5d9a330 100644
--- a/runner.go
+++ b/runner.go
@@ -210,12 +210,23 @@ func (r *Runner) runStepRequest(step *TStep) (stepData *StepData, err error) {
 		}
 		var dataBytes []byte
 		switch vv := data.(type) {
-		case map[string]interface{}: // post json
-			dataBytes, err = json.Marshal(vv)
-			if err != nil {
-				return nil, err
+		case map[string]interface{}:
+			contentType := req.Header.Get("Content-Type")
+			if strings.HasPrefix(contentType, "application/x-www-form-urlencoded") {
+				// post form data
+				formData := make(url.Values)
+				for k, v := range vv {
+					formData.Add(k, fmt.Sprint(v))
+				}
+				dataBytes = []byte(formData.Encode())
+			} else {
+				// post json
+				dataBytes, err = json.Marshal(vv)
+				if err != nil {
+					return nil, err
+				}
+				req.Header.Set("Content-Type", "application/json; charset=UTF-8")
 			}
-			setContentType(req, "application/json; charset=UTF-8")
 		case string:
 			dataBytes = []byte(vv)
 		case []byte:
@@ -237,7 +248,6 @@ func (r *Runner) runStepRequest(step *TStep) (stepData *StepData, err error) {
 
 	// do request action
 	// req.Debug = r.debug
-	// resp, err := r.client.Do(string(step.Request.Method), step.Request.URL, v...)
 
 	resp, err := r.client.Do(req)
 	if err != nil {
@@ -315,9 +325,3 @@ func setBodyBytes(req *http.Request, data []byte) {
 	req.Body = ioutil.NopCloser(bytes.NewReader(data))
 	req.ContentLength = int64(len(data))
 }
-
-func setContentType(req *http.Request, contentType string) {
-	if req.Header.Get("Content-Type") == "" {
-		req.Header.Set("Content-Type", contentType)
-	}
-}