diff --git a/libraries/mogo-adas-data/src/main/proto/message_pad.proto b/libraries/mogo-adas-data/src/main/proto/message_pad.proto
index 0f21c4ba3a..907fc0ead6 100644
--- a/libraries/mogo-adas-data/src/main/proto/message_pad.proto
+++ b/libraries/mogo-adas-data/src/main/proto/message_pad.proto
@@ -147,7 +147,7 @@ message RouteInfo{
     Location endLocation = 3;
     string endName = 4;
     repeated Location wayPoints = 5;
-    double speedLimit = 6;
+    double speedLimit = 6; //单位: km/h
     uint32 vehicleType = 7;
     bool isSpeakVoice = 8;
 }