diff --git a/registry/servicediscovery/service_discovery_registry.go b/registry/servicediscovery/service_discovery_registry.go
index 6d07dd318e..45562c55bc 100644
--- a/registry/servicediscovery/service_discovery_registry.go
+++ b/registry/servicediscovery/service_discovery_registry.go
@@ -19,6 +19,7 @@ package servicediscovery
 
 import (
 	"errors"
+	"sort"
 	"strconv"
 	"strings"
 	"sync"
@@ -194,8 +195,7 @@ func (s *serviceDiscoveryRegistry) UnSubscribe(url *common.URL, listener registr
 	if services == nil {
 		return nil
 	}
-	// FIXME ServiceNames.String() is not good
-	serviceNamesKey := services.String()
+	serviceNamesKey := sortServices(services)
 	l := s.serviceListeners[serviceNamesKey]
 	if l != nil {
 		l.RemoveListener(url.ServiceKey())
@@ -350,9 +350,8 @@ func (s *serviceDiscoveryRegistry) Subscribe(url *common.URL, notify registry.No
 }
 
 func (s *serviceDiscoveryRegistry) SubscribeURL(url *common.URL, notify registry.NotifyListener, services *gxset.HashSet) {
-	// FIXME ServiceNames.String() is not good
 	var err error
-	serviceNamesKey := services.String()
+	serviceNamesKey := sortServices(services)
 	protocol := constant.TriProtocol // consume "tri" protocol by default, other protocols need to be specified on reference/consumer explicitly
 	if url.Protocol != "" {
 		protocol = url.Protocol
@@ -392,6 +391,17 @@ func (s *serviceDiscoveryRegistry) SubscribeURL(url *common.URL, notify registry
 	}()
 }
 
+func sortServices(services *gxset.HashSet) string {
+	list := make([]string, 0, services.Size())
+	for _, v := range services.Values() {
+		if s, ok := v.(string); ok && s != "" {
+			list = append(list, s)
+		}
+	}
+	sort.Strings(list)
+	return strings.Join(list, ",")
+}
+
 // LoadSubscribeInstances load subscribe instance
 func (s *serviceDiscoveryRegistry) LoadSubscribeInstances(url *common.URL, notify registry.NotifyListener) error {
 	return nil