diff --git a/kernel/model/flashcard.go b/kernel/model/flashcard.go
index d0806acca..7e8022c74 100644
--- a/kernel/model/flashcard.go
+++ b/kernel/model/flashcard.go
@@ -76,27 +76,20 @@ func countTreeFlashcard(rootID string, deck *riff.Deck, deckBlockIDs []string) (
 }
 
 func countBoxFlashcard(boxID string, deck *riff.Deck, deckBlockIDs []string) (newFlashcardCount, dueFlashcardCount, flashcardCount int) {
-	entries, err := os.ReadDir(filepath.Join(util.DataDir, boxID))
-	if nil != err {
-		logging.LogErrorf("read dir failed: %s", err)
+	blockIDs := getBoxBlocks(boxID)
+	for _, blockID := range deckBlockIDs {
+		if gulu.Str.Contains(blockID, blockIDs) {
+			flashcardCount++
+		}
+	}
+	if 1 > flashcardCount {
 		return
 	}
 
-	for _, entry := range entries {
-		if entry.IsDir() {
-			continue
-		}
-
-		if !strings.HasSuffix(entry.Name(), ".sy") {
-			continue
-		}
-
-		rootID := strings.TrimSuffix(entry.Name(), ".sy")
-		treeNewFlashcardCount, treeDueFlashcardCount, treeFlashcardCount := countTreeFlashcard(rootID, deck, deckBlockIDs)
-		flashcardCount += treeFlashcardCount
-		newFlashcardCount += treeNewFlashcardCount
-		dueFlashcardCount += treeDueFlashcardCount
-	}
+	newFlashCards := deck.GetNewCardsByBlockIDs(blockIDs)
+	newFlashcardCount = len(newFlashCards)
+	newDueFlashcards := deck.GetDueCardsByBlockIDs(blockIDs)
+	dueFlashcardCount = len(newDueFlashcards)
 	return
 }
 
@@ -421,6 +414,14 @@ func getTreeSubTreeChildBlocks(rootID string) (treeBlockIDs []string) {
 	return
 }
 
+func getBoxBlocks(boxID string) (blockIDs []string) {
+	bts := treenode.GetBlockTreesByBoxID(boxID)
+	for _, bt := range bts {
+		blockIDs = append(blockIDs, bt.ID)
+	}
+	return
+}
+
 func GetDueFlashcards(deckID string, reviewedCardIDs []string) (ret []*Flashcard, unreviewedCount int, err error) {
 	deckLock.Lock()
 	defer deckLock.Unlock()
diff --git a/kernel/treenode/blocktree.go b/kernel/treenode/blocktree.go
index 045a7f35c..01dab254e 100644
--- a/kernel/treenode/blocktree.go
+++ b/kernel/treenode/blocktree.go
@@ -255,6 +255,21 @@ func RemoveBlockTreesByPathPrefix(pathPrefix string) {
 	}
 }
 
+func GetBlockTreesByBoxID(boxID string) (ret []*BlockTree) {
+	blockTrees.Range(func(key, value interface{}) bool {
+		slice := value.(*btSlice)
+		slice.m.Lock()
+		for _, b := range slice.data {
+			if b.BoxID == boxID {
+				ret = append(ret, b)
+			}
+		}
+		slice.m.Unlock()
+		return true
+	})
+	return
+}
+
 func RemoveBlockTreesByBoxID(boxID string) (ids []string) {
 	blockTrees.Range(func(key, value interface{}) bool {
 		slice := value.(*btSlice)