diff --git a/docs/developer_guides/chap07_query_coordinator.md b/docs/developer_guides/chap07_query_coordinator.md
index de6ae398bf..067b2d534b 100644
--- a/docs/developer_guides/chap07_query_coordinator.md
+++ b/docs/developer_guides/chap07_query_coordinator.md
@@ -246,6 +246,7 @@ type QueryNode interface {
 	AddQueryChannel(ctx context.Context, req *querypb.AddQueryChannelRequest) (*commonpb.Status, error)
   // RemoveQueryChannel removes the query channel for QueryNode component.
 	RemoveQueryChannel(ctx context.Context, req *querypb.RemoveQueryChannelRequest) (*commonpb.Status, error)
+  // WatchDmChannels watches the channels about data manipulation.
 	WatchDmChannels(ctx context.Context, req *querypb.WatchDmChannelsRequest) (*commonpb.Status, error)
 	// LoadSegments notifies QueryNode to load the sealed segments from storage. The load tasks are sync to this
 	// rpc, QueryNode will return after all the sealed segments are loaded.