Hello, @LIAOQIN,
Your issue has been solved, please check back to your site now after removing the browser cache. You have chosen the single post layout as the sidebar layout and there was no widget in that sidebar and that is why it picks the default search widget for that sidebar.
I just changed the layout as without a sidebar and it resolved the issue.
https://postimg.cc/CZ0rMcxk
https://postimg.cc/NyPXC0SF
Regards 8Themes Team.