diff --git a/index/index.go b/index/index.go
index a1ea224..be76f68 100644
--- a/index/index.go
+++ b/index/index.go
@@ -16,11 +16,20 @@ const (
 	Composite   IndexType = "composite"
 )
 
+// IndexSortOrder 表示索引的排序方式
+type IndexSortOrder string
+
+const (
+	Ascending  IndexSortOrder = "asc"
+	Descending IndexSortOrder = "desc"
+)
+
 // IndexMetadata 索引元数据
 type IndexMetadata struct {
-	Name      string
-	Type      IndexType
-	KeyFields []string
+	Name       string
+	Type       IndexType
+	KeyFields  []string
+	SortOrders []IndexSortOrder // 每个字段对应的排序方式（长度应与KeyFields一致）
 }
 
 // IndexStore 管理索引的存储和查询
@@ -38,12 +47,18 @@ func NewIndexStore(path string) (*IndexStore, error) {
 }
 
 // CreateIndex 创建索引
-func (is *IndexStore) CreateIndex(indexName string, indexType IndexType, keyFields []string) error {
+func (is *IndexStore) CreateIndex(indexName string, indexType IndexType, keyFields []string, sortOrders []IndexSortOrder) error {
+	// 验证keyFields和sortOrders长度一致
+	if len(keyFields) != len(sortOrders) {
+		return fmt.Errorf("keyFields and sortOrders must have the same length")
+	}
+
 	// 存储索引元数据
 	metadata := IndexMetadata{
-		Name:      indexName,
-		Type:      indexType,
-		KeyFields: keyFields,
+		Name:       indexName,
+		Type:       indexType,
+		KeyFields:  keyFields,
+		SortOrders: sortOrders, // 使用字段级排序方式
 	}
 
 	data, err := bson.Marshal(metadata)
diff --git a/index/index_test.go b/index/index_test.go
index a4a8c94..7d32362 100644
--- a/index/index_test.go
+++ b/index/index_test.go
@@ -23,8 +23,8 @@ func TestIndexStore(t *testing.T) {
 	indexName := "test_index"
 	keyFields := []string{"name"}
 
-	// 测试创建索引
-	if err := is.CreateIndex(indexName, SingleField, keyFields); err != nil {
+	// 测试创建索引（默认升序）
+	if err := is.CreateIndex(indexName, SingleField, keyFields, []IndexSortOrder{Ascending}); err != nil {
 		t.Errorf("CreateIndex failed: %v", err)
 	}
 
@@ -66,8 +66,8 @@ func TestCompositeIndex(t *testing.T) {
 	indexName := "composite_index"
 	keyFields := []string{"name", "age"}
 
-	// 创建复合索引
-	if err := is.CreateIndex(indexName, Composite, keyFields); err != nil {
+	// 创建复合索引（默认升序）
+	if err := is.CreateIndex(indexName, Composite, keyFields, []IndexSortOrder{Ascending, Ascending}); err != nil {
 		t.Errorf("CreateIndex failed: %v", err)
 	}
 
@@ -82,6 +82,91 @@ func TestCompositeIndex(t *testing.T) {
 	}
 }
 
+func TestIndexSortOrder(t *testing.T) {
+	// 测试目录
+	dir := "./testdb_sort"
+	defer os.RemoveAll(dir)
+
+	// 初始化索引存储
+	is, err := NewIndexStore(dir)
+	if err != nil {
+		t.Fatalf("Failed to create index store: %v", err)
+	}
+	defer is.storage.Close()
+
+	// 测试单字段索引的排序
+	indexName := "sorted_index"
+	keyFields := []string{"timestamp"}
+
+	// 测试创建升序索引
+	if err := is.CreateIndex(indexName, SingleField, keyFields, []IndexSortOrder{Ascending}); err != nil {
+		t.Errorf("CreateIndex failed: %v", err)
+	}
+
+	// 验证元数据
+	metadata, err := is.GetIndexMetadata(indexName)
+	if err != nil {
+		t.Errorf("GetIndexMetadata failed: %v", err)
+	}
+
+	if len(metadata.SortOrders) != 1 || metadata.SortOrders[0] != Ascending {
+		t.Errorf("Expected sort order to be ascending, got %v", metadata.SortOrders)
+	}
+
+	// 测试创建降序索引
+	indexNameDesc := "sorted_index_desc"
+	if err := is.CreateIndex(indexNameDesc, SingleField, keyFields, []IndexSortOrder{Descending}); err != nil {
+		t.Errorf("CreateIndex failed: %v", err)
+	}
+
+	// 验证降序元数据
+	metadataDesc, err := is.GetIndexMetadata(indexNameDesc)
+	if err != nil {
+		t.Errorf("GetIndexMetadata failed: %v", err)
+	}
+
+	if len(metadataDesc.SortOrders) != 1 || metadataDesc.SortOrders[0] != Descending {
+		t.Errorf("Expected sort order to be descending, got %v", metadataDesc.SortOrders)
+	}
+}
+
+func TestCompositeIndexSortOrders(t *testing.T) {
+	// 测试复合索引的不同字段排序
+	dir := "./testdb_composite_sort"
+	defer os.RemoveAll(dir)
+
+	is, err := NewIndexStore(dir)
+	if err != nil {
+		t.Fatalf("Failed to create index store: %v", err)
+	}
+	defer is.storage.Close()
+
+	// 测试复合索引（不同字段不同排序）
+	indexName := "composite_index_mixed"
+	keyFields := []string{"name", "age"}
+	sortOrders := []IndexSortOrder{Descending, Ascending}
+
+	// 创建复合索引
+	if err := is.CreateIndex(indexName, Composite, keyFields, sortOrders); err != nil {
+		t.Errorf("CreateIndex failed: %v", err)
+	}
+
+	// 验证元数据
+	metadata, err := is.GetIndexMetadata(indexName)
+	if err != nil {
+		t.Errorf("GetIndexMetadata failed: %v", err)
+	}
+
+	if metadata.Type != Composite || len(metadata.KeyFields) != 2 {
+		t.Errorf("Composite index metadata mismatch: got %+v want type=%s fieldsCount=2", metadata, Composite)
+	}
+
+	// 验证每个字段的排序方式
+	if metadata.SortOrders[0] != Descending || metadata.SortOrders[1] != Ascending {
+		t.Errorf("Expected sort orders [desc, asc], got [%v, %v]", metadata.SortOrders[0], metadata.SortOrders[1])
+	}
+}
+
 func BenchmarkSingleFieldQuery(b *testing.B) {
 	// 基准测试单字段查询性能
 	dir := "./testdb_bench"
@@ -91,7 +176,7 @@ func BenchmarkSingleFieldQuery(b *testing.B) {
 
 	// 创建测试数据
 	for i := 0; i < 1000; i++ {
-		is.CreateIndex(fmt.Sprintf("index_%d", i), SingleField, []string{"name"})
+		is.CreateIndex(fmt.Sprintf("index_%d", i), SingleField, []string{"name"}, []IndexSortOrder{Ascending})
 	}
 
 	b.ResetTimer()
@@ -120,8 +205,8 @@ func TestConcurrentIndexOperations(t *testing.T) {
 			defer wg.Done()
 			indexName := fmt.Sprintf("concurrent_index_%d", i)
 
-			// 创建索引
-			if err := is.CreateIndex(indexName, SingleField, []string{"name"}); err != nil {
+			// 创建索引（默认升序）
+			if err := is.CreateIndex(indexName, SingleField, []string{"name"}, []IndexSortOrder{Ascending}); err != nil {
 				t.Errorf("CreateIndex failed: %v", err)
 			}
 
@@ -133,4 +218,4 @@ func TestConcurrentIndexOperations(t *testing.T) {
 	}
 
 	wg.Wait()
-}
\ No newline at end of file
+}