diff --git a/kernel/model/flashcard.go b/kernel/model/flashcard.go
index 45ecb70a1..6f614596e 100644
--- a/kernel/model/flashcard.go
+++ b/kernel/model/flashcard.go
@@ -33,7 +33,6 @@ import (
 	"github.com/siyuan-note/logging"
 	"github.com/siyuan-note/riff"
 	"github.com/siyuan-note/siyuan/kernel/cache"
-	"github.com/siyuan-note/siyuan/kernel/filesys"
 	"github.com/siyuan-note/siyuan/kernel/sql"
 	"github.com/siyuan-note/siyuan/kernel/treenode"
 	"github.com/siyuan-note/siyuan/kernel/util"
@@ -367,32 +366,9 @@ func getTreeSubTreeChildBlocks(rootID string) (treeBlockIDs []string) {
 		return
 	}
 
-	trees := []*parse.Tree{tree}
-	box := Conf.Box(tree.Box)
-	luteEngine := util.NewLute()
-	files := box.ListFiles(tree.Path)
-	for _, subFile := range files {
-		if !strings.HasSuffix(subFile.path, ".sy") {
-			continue
-		}
-
-		subTree, loadErr := filesys.LoadTree(box.ID, subFile.path, luteEngine)
-		if nil != loadErr {
-			continue
-		}
-
-		trees = append(trees, subTree)
-	}
-
-	for _, t := range trees {
-		ast.Walk(t.Root, func(n *ast.Node, entering bool) ast.WalkStatus {
-			if !entering || !n.IsBlock() {
-				return ast.WalkContinue
-			}
-
-			treeBlockIDs = append(treeBlockIDs, n.ID)
-			return ast.WalkContinue
-		})
+	bts := treenode.GetBlockTreesByPathPrefix(strings.TrimSuffix(tree.Path, ".sy"))
+	for _, bt := range bts {
+		treeBlockIDs = append(treeBlockIDs, bt.ID)
 	}
 	return
 }
diff --git a/kernel/treenode/blocktree.go b/kernel/treenode/blocktree.go
index d29aa48e6..ff0a0bc0e 100644
--- a/kernel/treenode/blocktree.go
+++ b/kernel/treenode/blocktree.go
@@ -180,6 +180,21 @@ func RemoveBlockTreesByRootID(rootID string) {
 	}
 }
 
+func GetBlockTreesByPathPrefix(pathPrefix string) (ret []*BlockTree) {
+	blockTrees.Range(func(key, value interface{}) bool {
+		slice := value.(*btSlice)
+		slice.m.Lock()
+		for _, b := range slice.data {
+			if strings.HasPrefix(b.Path, pathPrefix) {
+				ret = append(ret, b)
+			}
+		}
+		slice.m.Unlock()
+		return true
+	})
+	return
+}
+
 func RemoveBlockTreesByPathPrefix(pathPrefix string) {
 	var ids []string
 	blockTrees.Range(func(key, value interface{}) bool {