diff --git a/api/server.go b/api/server.go
index beb1b76..c8798e2 100644
--- a/api/server.go
+++ b/api/server.go
@@ -36,12 +36,13 @@ func (s *ServerAPI) GetTraffic(stream TrojanServerService_GetTrafficServer) erro
 		if !valid {
 			stream.Send(&GetTrafficResponse{
 				Success: false,
-				Info:    "invalid user",
+				Info:    "invalid user " + req.User.Hash,
 			})
 			continue
 		}
 		downloadTraffic, uploadTraffic := meter.Get()
 		downloadSpeed, uploadSpeed := meter.GetSpeed()
+		downloadSpeedLimit, uploadSpeedLimit := meter.GetSpeedLimit()
 		err = stream.Send(&GetTrafficResponse{
 			Success: true,
 			TrafficTotal: &Traffic{
@@ -52,6 +53,10 @@ func (s *ServerAPI) GetTraffic(stream TrojanServerService_GetTrafficServer) erro
 				DownloadSpeed: downloadSpeed,
 				UploadSpeed:   uploadSpeed,
 			},
+			SpeedLimit: &Speed{
+				DownloadSpeed: uint64(downloadSpeedLimit),
+				UploadSpeed:   uint64(uploadSpeedLimit),
+			},
 		})
 		if err != nil {
 			return err
@@ -80,7 +85,12 @@ func (s *ServerAPI) SetUsers(stream TrojanServerService_SetUsersServer) error {
 		case SetUserRequest_Delete:
 			err = s.auth.DelUser(req.User.Hash)
 		case SetUserRequest_Modify:
-			err = common.NewError("not support yet")
+			valid, meter := s.auth.AuthUser(req.User.Hash)
+			if !valid {
+				err = common.NewError("invalid user " + req.User.Hash)
+			} else {
+				meter.LimitSpeed(int(req.SpeedLimit.DownloadSpeed), int(req.SpeedLimit.UploadSpeed))
+			}
 		}
 		if err != nil {
 			stream.Send(&SetUserResponse{
@@ -100,6 +110,7 @@ func (s *ServerAPI) ListUsers(req *ListUserRequest, stream TrojanServerService_L
 	for _, meter := range users {
 		downloadTraffic, uploadTraffic := meter.Get()
 		downloadSpeed, uploadSpeed := meter.GetSpeed()
+		downloadSpeedLimit, uploadSpeedLimit := meter.GetSpeedLimit()
 		err := stream.Send(&ListUserResponse{
 			User: &User{
 				Hash: meter.Hash(),
@@ -112,6 +123,10 @@ func (s *ServerAPI) ListUsers(req *ListUserRequest, stream TrojanServerService_L
 				DownloadSpeed: downloadSpeed,
 				UploadSpeed:   uploadSpeed,
 			},
+			SpeedLimit: &Speed{
+				DownloadSpeed: uint64(downloadSpeedLimit),
+				UploadSpeed:   uint64(uploadSpeedLimit),
+			},
 		})
 		if err != nil {
 			return err
diff --git a/api/server_test.go b/api/server_test.go
index 7f01ad8..c7e8d75 100644
--- a/api/server_test.go
+++ b/api/server_test.go
@@ -36,11 +36,12 @@ func TestServerAPI(t *testing.T) {
 		if resp.User.Hash != "hash1234" {
 			t.Fail()
 		}
+		fmt.Println(resp.SpeedCurrent)
+		fmt.Println(resp.SpeedLimit)
 	}
 	stream1.CloseSend()
-
 	meter.Count(1234, 5678)
-	time.Sleep(time.Millisecond * 400)
+	time.Sleep(time.Millisecond * 1000)
 	stream2, err := server.GetTraffic(ctx)
 	common.Must(err)
 	stream2.Send(&GetTrafficRequest{
@@ -56,7 +57,6 @@ func TestServerAPI(t *testing.T) {
 	if resp2.SpeedCurrent.DownloadSpeed != 1234 || resp2.TrafficTotal.UploadTraffic != 5678 {
 		t.Fail()
 	}
-	stream2.CloseSend()
 
 	stream3, err := server.SetUsers(ctx)
 	stream3.Send(&SetUserRequest{
@@ -83,9 +83,42 @@ func TestServerAPI(t *testing.T) {
 	if err != nil || !resp3.Success {
 		t.Fail()
 	}
-	valid, _ = auth.AuthUser("newhash")
+	valid, meter = auth.AuthUser("newhash")
 	if !valid {
 		t.Fail()
 	}
+	stream3.Send(&SetUserRequest{
+		User: &User{
+			Hash: "newhash",
+		},
+		Operation: SetUserRequest_Modify,
+		SpeedLimit: &Speed{
+			DownloadSpeed: 5000,
+			UploadSpeed:   3000,
+		},
+	})
+	go func() {
+		for {
+			meter.Count(200, 0)
+		}
+	}()
+	go func() {
+		for {
+			meter.Count(0, 300)
+		}
+	}()
+	time.Sleep(time.Second * 3)
+	for i := 0; i < 3; i++ {
+		stream2.Send(&GetTrafficRequest{
+			User: &User{
+				Hash: "newhash",
+			},
+		})
+		resp2, err = stream2.Recv()
+		fmt.Println(resp2.SpeedCurrent)
+		fmt.Println(resp2.SpeedLimit)
+		time.Sleep(time.Second)
+	}
+	stream2.CloseSend()
 	cancel()
 }
diff --git a/stat/memory/memory.go b/stat/memory/memory.go
index ec9070d..1539c1b 100644
--- a/stat/memory/memory.go
+++ b/stat/memory/memory.go
@@ -45,11 +45,11 @@ func (m *MemoryTrafficMeter) Count(sent, recv int) {
 	atomic.AddUint64(&m.recv, uint64(recv))
 }
 
-func (m *MemoryTrafficMeter) LimitSpeed(sent, recv int) {
-	if sent == 0 {
+func (m *MemoryTrafficMeter) LimitSpeed(send, recv int) {
+	if send == 0 {
 		m.sendLimiter = nil
 	} else {
-		m.sendLimiter = rate.NewLimiter(rate.Limit(sent), sent*2)
+		m.sendLimiter = rate.NewLimiter(rate.Limit(send), send*2)
 	}
 	if recv == 0 {
 		m.recvLimiter = nil
@@ -58,6 +58,18 @@ func (m *MemoryTrafficMeter) LimitSpeed(sent, recv int) {
 	}
 }
 
+func (m *MemoryTrafficMeter) GetSpeedLimit() (send, recv int) {
+	sendLimit := 0
+	recvLimit := 0
+	if m.sendLimiter != nil {
+		sendLimit = int(m.sendLimiter.Limit())
+	}
+	if m.recvLimiter != nil {
+		recvLimit = int(m.recvLimiter.Limit())
+	}
+	return sendLimit, recvLimit
+}
+
 func (m *MemoryTrafficMeter) Hash() string {
 	return m.hash
 }
diff --git a/stat/stat.go b/stat/stat.go
index d536bce..edec78b 100644
--- a/stat/stat.go
+++ b/stat/stat.go
@@ -11,12 +11,13 @@ import (
 type TrafficMeter interface {
 	io.Closer
 	Hash() string
-	Count(sent int, recv int)
-	Get() (sent uint64, recv uint64)
+	Count(sent, recv int)
+	Get() (sent, recv uint64)
 	Reset()
-	GetAndReset() (sent uint64, recv uint64)
-	GetSpeed() (sent uint64, recv uint64)
-	LimitSpeed(sent int, recv int)
+	GetAndReset() (sent, recv uint64)
+	GetSpeed() (sent, recv uint64)
+	LimitSpeed(send, recv int)
+	GetSpeedLimit() (send, recv int)
 }
 
 type Authenticator interface {