Considering the importance of grammatical aspect in writing process, this research is conducted to analyse grammatical errors in the writing of the first semester students of the English Education Department in Universitas Muhamadiyah Purwokerto. There are two research objectives of the study, the first being to describe the types of errors made by first semester students and the second being to find out highest of grammatical errors types. This is descriptive qualitative research. Documents of students’ writing were used as the source of data. The data were analyzed by using the theory of surface strategy taxonomy proposed by Dulay, Burt and Krashen. There were two kinds of data; qualitative and quantative. The qualitative data were presented in the description of each category of errors. Then, the quantitative data were presented in the form of frequency tables and charts for each category of surface strategy taxonomy. Based on the data analysis, four types of errors were found in students’ writing. They were 216 errors or 32.48% in omission, 267 errors or 40.15% in misformation,
162 errors or 24.36% in addition, and 20 errors or 3.01% in misordering. The highest frequency of error happens in misformation with 32.48% errors.