diff --git a/components/lib/treenode/TreeNode.d.ts b/components/lib/treenode/TreeNode.d.ts
index 4fad17535f..d0827ddace 100644
--- a/components/lib/treenode/TreeNode.d.ts
+++ b/components/lib/treenode/TreeNode.d.ts
@@ -13,7 +13,7 @@ export interface TreeNode {
     /**
      * Mandatory unique key of the node.
      */
-    key?: string;
+    key: string;
     /**
      * Label of the node.
      */