In this research, we gave a grammar test to students of the second semester, in total 50 questions, with the type of test « Closure test » in the matter of the passé composé and imparfait. Then, from the result of this test, we analyze the grammatical errors made by the students. So, this study entitled « Analysis of grammatical errors at past tenses by the students of the department of French UPI of second semester academic year 2017/2018 ». The purpose of this research is to describe grammatical errors made by the student. The research method used in this research is descriptive qualitative, and the dataswere obtained from the analysis of test results. Based on the analysis, we were able to conclude that the forms of errors are made by students is the conjugation error, the usage of auxiliary error, without the auxiliary, without agreement and error of the usage between the passé composé and imparfait in complex sentences and in a text. The main factor causing these errors is the neglect of students to answer questions and the lack of understanding of students to use the passé composé and imparfait in complex sentences and text.