Writing is an activity that cannot be separated from everyday life. However, there are still many people who do not know the true importance of having writing ability. It is really useful for finding the good method in learning writing for students. The research was focused to finding out that the diary writing can improve the students’ writing ability. This research used pre-experimental design to investigate the impact of diary method on students writing skill. This study used quantitative method were in the form of the results of the students’ writing before the implementation of the medium (pre-test) and after the implementation of the medium (post-test). Diary results were analyzed according to the five aspects of writing according to Brown (1993). The participants for the study were 29 students of class IX-1 of SMP Negeri 18
Banda Aceh. In this research, found that the students writing ability score has improvement
from 35 to 57,75. It is also found that t-table (2,75) < t-test (7,317) which means that there is significant difference between the results of pre-test and post-test. Therefore, it can be
concluded that diary method is able to improve students’ writing ability.