Punctuation marks,closely related to the contents of the article,play an irreplaceable role in the articles.In modern times,most researches only focus on the functions and regularities of punctuation mark development,while a few researches are about the punctuation mark errors,especially punctuation mark errors in English majors’writing.This thesis chooses English majors in USST(University of Shanghai for Science and Technology)as research subjects,investigates and analyzes the reasons for the punctuation mark errors,in an attempt to seek for implications to students’learning and English teaching.