This is a system that uses Pinyin as English to help you check spelling mistakes. This function can be turned off in the settings.

Forget the spell check.

Select the options in WPS text, select the Spelling tab in the dialog box that opens, and uncheck the check box before spelling check when typing and displaying ignored spelling errors in the document.

That's WORD's spelling check. If you don't want this red line, open WORD, choose Tools-Options-Spelling and Grammar, and check the box in front of the spelling check when typing.