Hi Tho Banh,
Welcome to Answers community.
May I confirm if you want to turn off AutoSave in Excel for the web or in the Excel workbook that you opened in desktop client from online location?
In Office for the web, when you make any edits, your changes are saved automatically so you don’t have to save your work manually and there’s no setting to disable this feature.
In desktop client, AutoSave is enabled when working on a file that is saved to OneDrive, OneDrive for Business, or SharePoint Online. If the file is saved to another location (or if it hasn't been saved at all, yet), then AutoSave is disabled.
If you turn AutoSave Off for an individual file, the program will remember to keep it off every time you reopen that file. If you switch it back On for an individual file, it will remember to keep in on for that file.
If you want to turn AutoSave off, by default, for all files, go to File > Options > Save and uncheck the box next to AutoSave OneDrive and SharePoint Online files by default on <application>.Restart Excel (or whichever application you're in) and the change will take effect.
Note*: If you want AutoSave off by default for all your Office applications, such as Word and Excel too, you'll need to repeat these steps for each of those programs.*
For more information, see What is AutoSave?
Let me know if you need any help. Have a nice day and stay safe😊
Regards,
Neha