Hi Mengfang Zhang,
Just so I understand correctly, it sounds like you already know how to set a default worksheet. It seems like you want to set a default page. Have you tried the documentation below?
Let me know if this helps.
This looks straightforward, but using Tableau Online, the option to "Set the Default Start Page for All Users" is not shown. Is there a way to avoid having all users land on the Workbooks page where they seem to be able to see everything, even when not granted permissions?