Investigating students’ grammatical knowledge through analyzing their writing is great importance for lectures to help them improve. In this research, the researcher will apply corpus linguistics as the method to analyze students’ writing. Corpus linguistics is the study of language data on a large scale, computerization data analysis of extensive collections of written text. This study is a Corpus – Based Study on The Use of the Verb II and auxiliary ‘Be’ Past Tense in Argumentative Essays of Indonesians EFL Learners (A case in Diploma III Kesekretariatan in Social and Politic Science Faculty (FISIP), Tanjungpura University, West Kalimantan, Indonesia. This study aims to investigate these matters more thoroughly and it will hopefully contribute to give future teachers a general idea on which grammatical points to focus on in their teaching of English grammar as a foreign language. There are four main research questions raise in this research, (1) the most dominant VVN tagset appear during this research; (2) the most dominant VBD tagset appear during this research; (3) the frequently errors made by students, whether the use of verb II or Auxiliary ‘Be’ Past Tense; and (4) the obstacles faced by students during writing an argumentative essay.  The findings showed there is an improvement in using Verb II and Auxiliary ‘Be’ past tense from cycle to cycle. Then the findings will leads the lectures and also the students to have more principle classroom activities and avoid students in make major mistake in argumentative writing.