Hello, Mr. Tim. Thanks for your reply. However, the problem seems not been raised by default settings. No matter how I change the font style, the letters will be shown as italic, but not regular. In addition, it is not only for the word but all the office software. For more detailed information, please refer to the following two pictures:
Actually, I found someone who got the same condition as mine. But his question also hasn't been solved. You can have a view of it for those specific methods that I tried.
It would be appreciated if you can check it over and find out the solution.