Arguing is a valuable competence that reveals a man’s intellectuality;
therefore, argumentative writing has been effectively applied into the syllabus
of many language universities. However, in fact, how to make a good
argumentative essay is really not easy to students. As a result, an investigation
into errors seems to be extremely significant. This paper, conducted to partly
improve the situation, is specificially aimed at figuring out the mistakes which
third year English Majors at Hai Phong Private University often commit and
their reasoning errors; thereby, the further step of proposing some ways to
decrease students’ errors can be done. To lay the theoretical foundation for
the paper, I did exhaustive research into literature with a range of relevant
works to provide readers with basics definitions of argument, logical errors
and argumentative essay respectively. Moreover, the main methodology
exploited by researcher is qualitative with the collection and in -depth analysis
of argumentative writing pieces of 83 students, interviews conducted among
10 participants and questionnaires given to 33 students