Hi @丰意 王 ,
There could be various reasons why the app pool needs to restart every time.
For example, if your site generates a specific number of errors in a specific amount of time then there is a feature(Rapid-Fail Protection) in the IIS that stops the app pool by itself.
You could try to check the Application, Security, and System Event Viewer logs. See whether it gives any information about the issue.
To get more information about how to check Event logs, you could refer to the links below.
If you find any helpful information in the Event logs then you could try to fix that issue and it could help prevent the issue. Else, you may need to provide more information about your site and issue. We could try to provide further suggestions.
If the issue is complex and you are not able to find the cause of the issue then I would suggest creating a Microsoft support ticket. Please note that it is a paid support.
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