diff --git a/builtin.go b/builtin.go
index cd0dd9a..cbb5ca9 100644
--- a/builtin.go
+++ b/builtin.go
@@ -51,7 +51,7 @@ var builtinFun BuiltinFunctions
 var builtinSel BuiltinSelections
 
 //builtin functions
-var builtinFuncMap = map[string]CallFunc{
+var builtinFuncs = map[string]CallFunc{
 	"absHref":       builtinFun.AbsHref,
 	"attr":          builtinFun.Attr,
 	"attrConcat":    builtinFun.AttrConcat,
@@ -94,5 +94,5 @@ var builtinFuncMap = map[string]CallFunc{
 //		return "Hello", nil
 //	})
 func (p *Pagser) RegisterFunc(name string, fn CallFunc) {
-	p.ctxFuncs[name] = fn
+	p.mapFuncs.Store(name, fn)
 }
diff --git a/pagser.go b/pagser.go
index 0f7ab9d..931225a 100644
--- a/pagser.go
+++ b/pagser.go
@@ -8,13 +8,18 @@
 
 package pagser
 
-import "errors"
+import (
+	"errors"
+	"sync"
+)
 
 // Pagser the page parser
 type Pagser struct {
-	Config   Config
-	ctxTags  map[string]*tagTokenizer // tag value => tagTokenizer
-	ctxFuncs map[string]CallFunc      // name => func
+	Config Config
+	//ctxTags  map[string]*tagTokenizer // tag value => tagTokenizer
+	mapTags sync.Map //map[string]*tagTokenizer
+	//ctxFuncs map[string]CallFunc      // name => func
+	mapFuncs sync.Map //map[string]CallFunc
 }
 
 // New create pagser client
@@ -31,9 +36,13 @@ func NewWithConfig(cfg Config) (*Pagser, error) {
 	if cfg.FuncSymbol == "" {
 		return nil, errors.New("FuncSymbol must not empty")
 	}
-	return &Pagser{
-		Config:   cfg,
-		ctxTags:  make(map[string]*tagTokenizer, 0),
-		ctxFuncs: builtinFuncMap,
-	}, nil
+	p := Pagser{
+		Config: cfg,
+		//mapTags:  make(map[string]*tagTokenizer, 0),
+		//mapFuncs: builtinFuncs,
+	}
+	for k, v := range builtinFuncs {
+		p.mapFuncs.Store(k, v)
+	}
+	return &p, nil
 }
diff --git a/parse.go b/parse.go
index 244f193..3ff6f7c 100644
--- a/parse.go
+++ b/parse.go
@@ -72,13 +72,16 @@ func (p *Pagser) doParse(v interface{}, stackRefValues []reflect.Value, selectio
 			continue
 		}
 
-		tag, ok := p.ctxTags[tagValue]
-		if !ok || tag == nil {
+		cacheTag, ok := p.mapTags.Load(tagValue)
+		var tag *tagTokenizer
+		if !ok || cacheTag == nil {
 			tag, err = p.newTag(tagValue)
 			if err != nil {
 				return err
 			}
-			p.ctxTags[tagValue] = tag
+			p.mapTags.Store(tagValue, tag)
+		} else {
+			tag = cacheTag.(*tagTokenizer)
 		}
 
 		node := selection
@@ -201,8 +204,9 @@ func (p *Pagser) findAndExecFunc(objRefValue reflect.Value, stackRefValues []ref
 		}
 
 		//global function
-		if fn, ok := p.ctxFuncs[selTag.FuncName]; ok {
-			outValue, err := fn(node, selTag.FuncParams...)
+		if fn, ok := p.mapFuncs.Load(selTag.FuncName); ok {
+			cfn := fn.(CallFunc)
+			outValue, err := cfn(node, selTag.FuncParams...)
 			if err != nil {
 				return nil, fmt.Errorf("call registered func %v error: %v", selTag.FuncName, err)
 			}
diff --git a/parse_test.go b/parse_test.go
index 458fe6a..2be808b 100644
--- a/parse_test.go
+++ b/parse_test.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net/http"
 	"strings"
+	"sync"
 	"testing"
 
 	"github.com/PuerkitoBio/goquery"
@@ -310,3 +311,23 @@ func TestPagser_ParseReader(t *testing.T) {
 	}
 	fmt.Printf("json: %v\n", prettyJson(data))
 }
+
+func TestPagser_RegisterFunc(t *testing.T) {
+	threads := 1000
+	p := New()
+	var wg sync.WaitGroup
+
+	for i := 0; i < threads; i++ {
+		wg.Add(1)
+		go func() {
+			for j := 0; j < 10; j++ {
+				for k, v := range builtinFuncs {
+					p.RegisterFunc(k, v)
+				}
+			}
+			wg.Done()
+		}()
+	}
+
+	wg.Wait()
+}