diff --git a/packages/frontend/core/src/blocksuite/view-extensions/code-block-preview/html-preview.ts b/packages/frontend/core/src/blocksuite/view-extensions/code-block-preview/html-preview.ts
index 4a390a15e..14f716c60 100644
--- a/packages/frontend/core/src/blocksuite/view-extensions/code-block-preview/html-preview.ts
+++ b/packages/frontend/core/src/blocksuite/view-extensions/code-block-preview/html-preview.ts
@@ -48,6 +48,7 @@ export class HTMLPreview extends SignalWatcher(WithDisposable(LitElement)) {
     .html-preview-iframe {
       width: 100%;
       height: 544px;
+      border: none;
     }
   `;