diff --git a/packages/frontend/core/src/blocksuite/extensions/code-block-preview/html-preview.ts b/packages/frontend/core/src/blocksuite/extensions/code-block-preview/html-preview.ts
index 027980418..4a390a15e 100644
--- a/packages/frontend/core/src/blocksuite/extensions/code-block-preview/html-preview.ts
+++ b/packages/frontend/core/src/blocksuite/extensions/code-block-preview/html-preview.ts
@@ -44,6 +44,11 @@ export class HTMLPreview extends SignalWatcher(WithDisposable(LitElement)) {
       font-weight: 400;
       line-height: normal;
     }
+
+    .html-preview-iframe {
+      width: 100%;
+      height: 544px;
+    }
   `;
 
   @property({ attribute: false })