diff --git a/internal/rootcoord/task.go b/internal/rootcoord/task.go
index dfe1577253..05d6028797 100644
--- a/internal/rootcoord/task.go
+++ b/internal/rootcoord/task.go
@@ -303,6 +303,17 @@ func (t *DropCollectionReqTask) Execute(ctx context.Context) error {
 		return err
 	}
 
+	// drop all indices
+	if err = t.core.RemoveIndex(ctx, t.Req.CollectionName, ""); err != nil {
+		return err
+	}
+
+	// Allocate a new ts to make sure the channel timetick is consistent.
+	ts, err = t.core.TSOAllocator(1)
+	if err != nil {
+		return fmt.Errorf("TSO alloc fail, error = %w", err)
+	}
+
 	// build DdOperation and save it into etcd, when ddmsg send fail,
 	// system can restore ddmsg from etcd and re-send
 	ddReq.Base.Timestamp = ts
@@ -311,11 +322,6 @@ func (t *DropCollectionReqTask) Execute(ctx context.Context) error {
 		return fmt.Errorf("encodeDdOperation fail, error = %w", err)
 	}
 
-	// drop all indices
-	if err = t.core.RemoveIndex(ctx, t.Req.CollectionName, ""); err != nil {
-		return err
-	}
-
 	// get all aliases before meta table updated
 	aliases := t.core.MetaTable.ListAliases(collMeta.ID)