After selecting a face , the bevel modifier works automatically , and can not quit it In edit mode, after selecting a face, blender automatically enters Bevel
and can not quit it. So I could not do anything else.
I reinstalled blender 2.81, the problem still happened.
Why?
Is there a possibility you might have changed a hotkey?

To be sure you have the factory settings, you can reset to factory preferences, to reset go to edit-> preferences-> click the 3 rows in the bottom left corner -> load factory preferences.