diff --git a/protocol/json/server_request.go b/protocol/json/server_request.go
index 0e1b593..ba90f3e 100644
--- a/protocol/json/server_request.go
+++ b/protocol/json/server_request.go
@@ -148,16 +148,21 @@ func (src *ServerRequestCodec) Params() ([]string, error) {
 
 		var results []string
 		for _, v := range values {
-			b, err := json.Marshal(v)
-			if nil != err {
-				src.err = &Error{
-					Code:    E_INVALID_REQ,
-					Message: err.Error(),
-					Data:    src.req.Params,
+			switch v := v.(type) {
+			case string:
+				results = append(results, v)
+			default:
+				b, err := json.Marshal(v)
+				if nil != err {
+					src.err = &Error{
+						Code:    E_INVALID_REQ,
+						Message: err.Error(),
+						Data:    src.req.Params,
+					}
+					return nil, src.err
 				}
-				return nil, src.err
+				results = append(results, string(b))
 			}
-			results = append(results, string(b))
 		}
 
 		return results, nil