diff --git a/kernel/model/file.go b/kernel/model/file.go
index b76449eaa..67c775cf9 100644
--- a/kernel/model/file.go
+++ b/kernel/model/file.go
@@ -1226,11 +1226,12 @@ func removeDoc(box *Box, p string) (err error) {
 
 	copyDocAssetsToDataAssets(box.ID, p)
 
-	rootID := tree.ID
 	var removeIDs []string
-	removeIDs = append(removeIDs, rootID)
+	ids := rootChildIDs(tree.ID)
+	removeIDs = append(removeIDs, ids...)
+
 	dir := path.Dir(p)
-	childrenDir := path.Join(dir, rootID)
+	childrenDir := path.Join(dir, tree.ID)
 	existChildren := box.Exist(childrenDir)
 	if existChildren {
 		absChildrenDir := filepath.Join(util.DataDir, tree.Box, childrenDir)
@@ -1242,8 +1243,6 @@ func removeDoc(box *Box, p string) (err error) {
 	indexHistoryDir(filepath.Base(historyDir), NewLute())
 
 	if existChildren {
-		ids := util.GetChildDocIDs(filepath.Join(util.DataDir, tree.Box, childrenDir))
-		removeIDs = append(removeIDs, ids...)
 		if err = box.Remove(childrenDir); nil != err {
 			return
 		}
diff --git a/kernel/util/path.go b/kernel/util/path.go
index 7249ab72a..54dad6677 100644
--- a/kernel/util/path.go
+++ b/kernel/util/path.go
@@ -202,22 +202,3 @@ func FilterSelfChildDocs(paths []string) (ret []string) {
 	}
 	return
 }
-
-func GetChildDocIDs(parentDocDirAbsPath string) (ret []string) {
-	if !gulu.File.IsDir(parentDocDirAbsPath) {
-		return
-	}
-
-	filepath.Walk(parentDocDirAbsPath, func(p string, info os.FileInfo, err error) error {
-		if info.IsDir() {
-			return nil
-		}
-		if !strings.HasSuffix(p, ".sy") {
-			return nil
-		}
-		id := strings.TrimSuffix(filepath.Base(p), ".sy")
-		ret = append(ret, id)
-		return nil
-	})
-	return
-}