diff --git a/config/config.go b/config/config.go
index 42df7fb0a..bd77a2e32 100644
--- a/config/config.go
+++ b/config/config.go
@@ -7,9 +7,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/go-kratos/kratos/v2/encoding"
-	// init json encoder
-	_ "github.com/go-kratos/kratos/v2/encoding/json"
 	"github.com/go-kratos/kratos/v2/log"
 )
 
@@ -20,8 +17,6 @@ var (
 	ErrTypeAssert = errors.New("type assert error")
 
 	_ Config = (*config)(nil)
-
-	codec = encoding.GetCodec("json")
 )
 
 // Observer is config observer.
@@ -125,7 +120,7 @@ func (c *config) Scan(v interface{}) error {
 	if err != nil {
 		return err
 	}
-	return codec.Unmarshal(data, v)
+	return unmarshalJSON(data, v)
 }
 
 func (c *config) Watch(key string, o Observer) error {
diff --git a/config/reader.go b/config/reader.go
index 601557eeb..637a5f524 100644
--- a/config/reader.go
+++ b/config/reader.go
@@ -1,10 +1,13 @@
 package config
 
 import (
+	"encoding/json"
 	"fmt"
 	"strings"
 
 	"github.com/imdario/mergo"
+	"google.golang.org/protobuf/encoding/protojson"
+	"google.golang.org/protobuf/proto"
 )
 
 // Reader is config reader.
@@ -71,16 +74,16 @@ func (r *reader) Value(path string) (Value, bool) {
 }
 
 func (r *reader) Source() ([]byte, error) {
-	return codec.Marshal(r.values)
+	return marshalJSON(r.values)
 }
 
 func cloneMap(src map[string]interface{}) (map[string]interface{}, error) {
-	data, err := codec.Marshal(src)
+	data, err := marshalJSON(src)
 	if err != nil {
 		return nil, err
 	}
 	dst := make(map[string]interface{})
-	if err = codec.Unmarshal(data, &dst); err != nil {
+	if err = unmarshalJSON(data, &dst); err != nil {
 		return nil, err
 	}
 	return dst, nil
@@ -104,3 +107,17 @@ func convertMap(src interface{}) interface{} {
 		return src
 	}
 }
+
+func marshalJSON(v interface{}) ([]byte, error) {
+	if m, ok := v.(proto.Message); ok {
+		return protojson.Marshal(m)
+	}
+	return json.Marshal(v)
+}
+
+func unmarshalJSON(data []byte, v interface{}) error {
+	if m, ok := v.(proto.Message); ok {
+		return protojson.Unmarshal(data, m)
+	}
+	return json.Unmarshal(data, v)
+}
diff --git a/encoding/json/json.go b/encoding/json/json.go
index 7f78063a2..1f57c2599 100644
--- a/encoding/json/json.go
+++ b/encoding/json/json.go
@@ -5,25 +5,11 @@ import (
 	"reflect"
 
 	"github.com/go-kratos/kratos/v2/encoding"
-
-	"google.golang.org/protobuf/encoding/protojson"
-	"google.golang.org/protobuf/proto"
 )
 
 // Name is the name registered for the json codec.
 const Name = "json"
 
-var (
-	// MarshalOptions is a configurable JSON format marshaler.
-	MarshalOptions = protojson.MarshalOptions{
-		EmitUnpopulated: true,
-	}
-	// UnmarshalOptions is a configurable JSON format parser.
-	UnmarshalOptions = protojson.UnmarshalOptions{
-		DiscardUnknown: true,
-	}
-)
-
 func init() {
 	encoding.RegisterCodec(codec{})
 }
@@ -32,24 +18,18 @@ func init() {
 type codec struct{}
 
 func (codec) Marshal(v interface{}) ([]byte, error) {
-	if m, ok := v.(proto.Message); ok {
-		return MarshalOptions.Marshal(m)
-	}
 	return json.Marshal(v)
 }
 
 func (codec) Unmarshal(data []byte, v interface{}) error {
 	rv := reflect.ValueOf(v)
 	for rv.Kind() == reflect.Ptr {
-		if rv.IsNil() {
+		if rv.IsNil() && rv.CanSet() {
 			rv.Set(reflect.New(rv.Type().Elem()))
 			v = rv.Interface()
 		}
 		rv = rv.Elem()
 	}
-	if m, ok := v.(proto.Message); ok {
-		return UnmarshalOptions.Unmarshal(data, m)
-	}
 	return json.Unmarshal(data, v)
 }