diff --git a/hrp/boomer.go b/hrp/boomer.go
index f66679d3..0e74fe5d 100644
--- a/hrp/boomer.go
+++ b/hrp/boomer.go
@@ -5,7 +5,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/jinzhu/copier"
 	"github.com/rs/zerolog/log"
 
 	"github.com/httprunner/funplugin"
@@ -98,27 +97,21 @@ func (b *HRPBoomer) convertBoomerTask(testcase *TestCase, rendezvousList []*Rend
 		Name:   config.Name,
 		Weight: config.Weight,
 		Fn: func() {
-			sessionTestCase := &TestCase{}
-			// copy testcase to avoid data racing
-			if err := copier.Copy(sessionTestCase, testcase); err != nil {
-				log.Error().Err(err).Msg("copy testcase data failed")
-				return
-			}
-			sessionRunner := hrpRunner.NewSessionRunner(sessionTestCase)
+			sessionRunner := hrpRunner.NewSessionRunner(testcase)
 			sessionRunner.parser.plugin = plugin
 
 			testcaseSuccess := true       // flag whole testcase result
 			var transactionSuccess = true // flag current transaction result
 
-			cfg := sessionTestCase.Config
+			var parameterVariables map[string]interface{}
 			// iterate through all parameter iterators and update case variables
-			for _, it := range cfg.ParametersSetting.Iterators {
+			for _, it := range testcase.Config.ParametersSetting.Iterators {
 				if it.HasNext() {
-					cfg.Variables = mergeVariables(it.Next(), cfg.Variables)
+					parameterVariables = it.Next()
 				}
 			}
 
-			if err := sessionRunner.parseConfig(cfg); err != nil {
+			if err := sessionRunner.parseConfig(parameterVariables); err != nil {
 				log.Error().Err(err).Msg("parse config failed")
 				return
 			}
diff --git a/hrp/session.go b/hrp/session.go
index 05173830..f59e6d01 100644
--- a/hrp/session.go
+++ b/hrp/session.go
@@ -4,6 +4,7 @@ import (
 	_ "embed"
 	"time"
 
+	"github.com/jinzhu/copier"
 	"github.com/pkg/errors"
 	"github.com/rs/zerolog/log"
 )
@@ -14,6 +15,7 @@ type SessionRunner struct {
 	testCase         *TestCase
 	hrpRunner        *HRPRunner
 	parser           *Parser
+	parsedConfig     *TConfig
 	sessionVariables map[string]interface{}
 	// transactions stores transaction timing info.
 	// key is transaction name, value is map of transaction type and time, e.g. start time and end time.
@@ -24,10 +26,10 @@ type SessionRunner struct {
 
 func (r *SessionRunner) init() {
 	log.Info().Msg("init session runner")
+	r.parsedConfig = &TConfig{}
 	r.sessionVariables = make(map[string]interface{})
 	r.transactions = make(map[string]map[transactionType]time.Time)
 	r.startTime = time.Now()
-	r.summary.Name = r.testCase.Config.Name
 }
 
 func (r *SessionRunner) GetParser() *Parser {
@@ -35,7 +37,7 @@ func (r *SessionRunner) GetParser() *Parser {
 }
 
 func (r *SessionRunner) GetConfig() *TConfig {
-	return r.testCase.Config
+	return r.parsedConfig
 }
 
 func (r *SessionRunner) LogOn() bool {
@@ -62,7 +64,7 @@ func (r *SessionRunner) Start() error {
 	}()
 
 	// parse config
-	if err := r.parseConfig(config); err != nil {
+	if err := r.parseConfig(nil); err != nil {
 		return err
 	}
 
@@ -105,56 +107,67 @@ func (r *SessionRunner) MergeStepVariables(vars map[string]interface{}) (map[str
 	// step variables > session variables (extracted variables from previous steps)
 	overrideVars := mergeVariables(vars, r.sessionVariables)
 	// step variables > testcase config variables
-	overrideVars = mergeVariables(overrideVars, r.testCase.Config.Variables)
+	overrideVars = mergeVariables(overrideVars, r.parsedConfig.Variables)
 
 	// parse step variables
 	parsedVariables, err := r.parser.ParseVariables(overrideVars)
 	if err != nil {
-		log.Error().Interface("variables", r.testCase.Config.Variables).
+		log.Error().Interface("variables", r.parsedConfig.Variables).
 			Err(err).Msg("parse step variables failed")
 		return nil, err
 	}
 	return parsedVariables, nil
 }
 
-func (r *SessionRunner) parseConfig(cfg *TConfig) error {
+// parseConfig parses testcase config with given variables, stores to parsedConfig.
+func (r *SessionRunner) parseConfig(variables map[string]interface{}) error {
+	cfg := r.testCase.Config
+
+	// deep copy config to avoid data racing
+	if err := copier.Copy(r.parsedConfig, cfg); err != nil {
+		log.Error().Err(err).Msg("copy testcase config failed")
+		return err
+	}
+
 	// parse config variables
-	parsedVariables, err := r.parser.ParseVariables(cfg.Variables)
+	mergedVars := mergeVariables(variables, cfg.Variables)
+	parsedVariables, err := r.parser.ParseVariables(mergedVars)
 	if err != nil {
 		log.Error().Interface("variables", cfg.Variables).Err(err).Msg("parse config variables failed")
 		return err
 	}
-	cfg.Variables = parsedVariables
+	r.parsedConfig.Variables = parsedVariables
 
 	// parse config name
 	parsedName, err := r.parser.ParseString(cfg.Name, cfg.Variables)
 	if err != nil {
 		return err
 	}
-	cfg.Name = convertString(parsedName)
+	r.parsedConfig.Name = convertString(parsedName)
 
 	// parse config base url
 	parsedBaseURL, err := r.parser.ParseString(cfg.BaseURL, cfg.Variables)
 	if err != nil {
 		return err
 	}
-	cfg.BaseURL = convertString(parsedBaseURL)
+	r.parsedConfig.BaseURL = convertString(parsedBaseURL)
 
 	// ensure correction of think time config
-	cfg.ThinkTimeSetting.checkThinkTime()
+	r.parsedConfig.ThinkTimeSetting.checkThinkTime()
 
 	return nil
 }
 
 func (r *SessionRunner) GetSummary() *TestCaseSummary {
 	caseSummary := r.summary
+	caseSummary.Name = r.parsedConfig.Name
 	caseSummary.Time.StartAt = r.startTime
 	caseSummary.Time.Duration = time.Since(r.startTime).Seconds()
 	exportVars := make(map[string]interface{})
-	for _, value := range r.testCase.Config.Export {
+	for _, value := range r.parsedConfig.Export {
 		exportVars[value] = r.sessionVariables[value]
 	}
 	caseSummary.InOut.ExportVars = exportVars
-	caseSummary.InOut.ConfigVars = r.testCase.Config.Variables
+	caseSummary.InOut.ConfigVars = r.parsedConfig.Variables
 	return caseSummary
 }
diff --git a/hrp/step_request_test.go b/hrp/step_request_test.go
index 50becbec..ae61fa2c 100644
--- a/hrp/step_request_test.go
+++ b/hrp/step_request_test.go
@@ -81,6 +81,7 @@ func TestRunRequestRun(t *testing.T) {
 	}
 	runner := NewRunner(t).SetRequestsLogOn()
 	sessionRunner := runner.NewSessionRunner(testcase)
+	sessionRunner.parseConfig(nil)
 	if _, err := stepGET.Run(sessionRunner); err != nil {
 		t.Fatalf("stepGET.Run() error: %v", err)
 	}
diff --git a/hrp/step_testcase.go b/hrp/step_testcase.go
index 031133a5..4692be58 100644
--- a/hrp/step_testcase.go
+++ b/hrp/step_testcase.go
@@ -55,18 +55,24 @@ func (s *StepTestCaseWithOptionalArgs) Run(r *SessionRunner) (*StepResult, error
 		return stepResult, err
 	}
 
-	// copy step to avoid data racing
-	copiedStep := &TStep{}
-	if err := copier.Copy(copiedStep, s.step); err != nil {
-		log.Error().Err(err).Msg("copy step failed")
+	stepTestCase := s.step.TestCase.(*TestCase)
+
+	// copy testcase to avoid data racing
+	copiedTestCase := &TestCase{}
+	if err := copier.Copy(copiedTestCase, stepTestCase); err != nil {
+		log.Error().Err(err).Msg("copy step testcase failed")
 		return stepResult, err
 	}
 
-	copiedStep.Variables = stepVariables
-	copiedTestCase := copiedStep.TestCase.(*TestCase)
-
 	// override testcase config
-	extendWithTestCase(s.step, copiedTestCase)
+	// override testcase name
+	if s.step.Name != "" {
+		copiedTestCase.Config.Name = s.step.Name
+	}
+	// merge & override variables
+	copiedTestCase.Config.Variables = mergeVariables(stepVariables, copiedTestCase.Config.Variables)
+	// merge & override extractors
+	copiedTestCase.Config.Export = mergeSlices(s.step.Export, copiedTestCase.Config.Export)
 
 	sessionRunner := r.hrpRunner.NewSessionRunner(copiedTestCase)
 
@@ -84,11 +90,6 @@ func (s *StepTestCaseWithOptionalArgs) Run(r *SessionRunner) (*StepResult, error
 	stepResult.ExportVars = summary.InOut.ExportVars
 	stepResult.Success = true
 
-	// update extracted variables
-	for k, v := range stepResult.ExportVars {
-		r.sessionVariables[k] = v
-	}
-
 	// merge testcase summary
 	r.summary.Records = append(r.summary.Records, summary.Records...)
 	r.summary.Stat.Total += summary.Stat.Total
@@ -97,15 +98,3 @@ func (s *StepTestCaseWithOptionalArgs) Run(r *SessionRunner) (*StepResult, error
 
 	return stepResult, nil
 }
-
-// extend referenced testcase with teststep, teststep config merge and override referenced testcase config
-func extendWithTestCase(testStep *TStep, overriddenTestCase *TestCase) {
-	// override testcase name
-	if testStep.Name != "" {
-		overriddenTestCase.Config.Name = testStep.Name
-	}
-	// merge & override variables
-	overriddenTestCase.Config.Variables = mergeVariables(testStep.Variables, overriddenTestCase.Config.Variables)
-	// merge & override extractors
-	overriddenTestCase.Config.Export = mergeSlices(testStep.Export, overriddenTestCase.Config.Export)
-}
diff --git a/hrp/step_thinktime.go b/hrp/step_thinktime.go
index ad158061..9abb20d5 100644
--- a/hrp/step_thinktime.go
+++ b/hrp/step_thinktime.go
@@ -38,7 +38,7 @@ func (s *StepThinkTime) Run(r *SessionRunner) (*StepResult, error) {
 		Success:  true,
 	}
 
-	cfg := r.testCase.Config.ThinkTimeSetting
+	cfg := r.parsedConfig.ThinkTimeSetting
 	if cfg == nil {
 		cfg = &ThinkTimeConfig{thinkTimeDefault, nil, 0}
 	}