Writing is a significant part of English teaching and learning, so it is worth analyzing and discussing. For middle school students in China, English writing takes up a noticeable proportion of 12.5 percent in the entrance examination for high schools, and it is indispensable in English learning. Moreover, it can effectively promote the internalization of students’ English knowledge and help test learners’ use of syntactic structure and words. Therefore, writing is as important as listening, speaking, and reading. However, writing is considered to be an obstacle to English education in China, and it seems to be overlooked in middle school English teaching compared to other major English skills. Chinese students’ actual writing ability falls far short of the requirements and standards. The purpose of the study is to identify grammar issues in Chinese middle school students’ English compositions from the perspective of Systematic Functional Linguistic. The study also aims to explore the process in which the teacher teaches writing and then provide some suggestions to help middle school teachers know how to model writing teaching and teach grammar so as to help students improve their writing abilities.