diff --git a/src/tree/TreeItem.tsx b/src/tree/TreeItem.tsx
index 2f7b70a895..6741a386a4 100644
--- a/src/tree/TreeItem.tsx
+++ b/src/tree/TreeItem.tsx
@@ -340,7 +340,9 @@ const TreeItem = forwardRef(
         data-value={node.value}
         data-level={level}
         className={classNames(treeClassNames.treeNode, {
-          [treeClassNames.treeNodeOpen]: node.expanded,
+          [treeClassNames.treeNodeOpen]:
+            node.expanded &&
+            (typeof node.data.children === 'boolean' ? node.data.children : node.data.children !== undefined),
           [treeClassNames.actived]: node.isActivable() ? node.actived : false,
           [treeClassNames.disabled]: node.isDisabled(),
           [treeClassNames.treeNodeDraggable]: node.isDraggable(),
diff --git a/src/tree/__tests__/tree.test.tsx b/src/tree/__tests__/tree.test.tsx
index 4cafa5dadc..2dea5c0542 100644
--- a/src/tree/__tests__/tree.test.tsx
+++ b/src/tree/__tests__/tree.test.tsx
@@ -197,6 +197,20 @@ describe('Tree test', () => {
     expect(onChangeFn1).not.toHaveBeenCalled();
   });
 
+  it('should calculate right class of tree item.', async () => {
+    const { container } = await renderTreeWithProps({
+      expanded: [1, '1-2', '1-2', 2],
+    });
+
+    await mockDelay(300);
+    const allItems = container.querySelectorAll('.t-tree__item');
+    expect(allItems.length).toBe(4);
+    const nodeOpenItems = container.querySelectorAll('.t-tree__item--open');
+    // only set expanded when node has children
+    // or children is `true` when the tree is lazy
+    expect(nodeOpenItems.length).toBe(1);
+  });
+
   test('props.line', async () => {
     const data = [
       {