As long as it is a graduation thesis for English majors, it is usually written in English. But it still depends on the requirements of your school or department.

Regarding the graduation thesis, the following is the expression of the 2000 edition of English Teaching Syllabus for English Majors in Colleges and Universities:

Graduation thesis is an important way to examine students' comprehensive ability and evaluate their academic achievements. Graduation thesis is generally written in English, with a length of 3000-5000 words. It requires fluent writing and ideas. ...

LZ can also consult online.