【Abstract】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.
　　【Key words】punctuation mark； error analysis； English major
　　As language learners， English major students not only need to master the knowledge of vocabulary and grammar， but also are required to grasp all aspects of professional knowledge. However， punctuation marks don’t get deserved attention，， on the contrary， are neglected. Researchers who study the punctuation errors in EFL learners’ writing only regard middle school students or college English learners as subjects （Lv Yan， 2006）. A fact exists that various punctuation mark errors can be seen in the writing of English majors， so it is imperative to find factors of punctuation mark.
　　1. The design of the research and methodology
　　In order to reveal the status quo of the punctuation mark use of English majors， error analysis is employed.
　　Research questions：
　　（1） What are the punctuation mark errors that English majors make？
　　（2） What is the frequency of each kind of error？
　　（3） What are possible reasons for the errors？
　　Data collection
　　The research employs corpus-based approach and develops with the aid of antconc.exe corpus analysis software. Corpus is set up by collecting compositions of English majors from Class 2010， Class 2011 and Class 2012. Five hundred and nine compositions （the total number of words is 152， 291） written by English majors in English writing course and integrated English course are collected. All of the selected compositions are scored and scores take up 30% of the final grades. Students attach much importance to these compositions. After studying the selected compositions， it shows that punctuation mark errors of overuse， absence and misuse all appear in the writing of students.
　　1.1 Punctuation overuse
　　Punctuation overuse refers to an error that learners put a punctuation mark in the place where it is unnecessary， mainly covering the following errors.