Reniasih Nurjayanti. 2013002089. The Use of Cooperative Learning Method to Improve Grammar Ability for the Eighth Grade Students of SMPN 3 Kutowinangun in the Academic Year 2018/2019. Yogyakarta : Universitas Sarjanawiyata Tamansiswa.The purpose of this research is to improve the grammar ability of the eighth grade students of SMPN 3 Kutowinangun in the academic year 2018/2019 through the use of cooperative learning method.The design of this research is an action research. The respondens of the study in this research were the eighth grade students of SMPN 3 Kutowinangun, and an English teacher as the collaborator. The data collection was done through observation, interviews, and grammar ability tests.The data analysis used qualitative steps. The process was begun from plan, action and reflection.The result of this research showed that the implementation of teaching grammar ability using coopearative learning methodof the students at the eighth grade of SMPN 3 Kutowinangun was able to improve the students’ grammar ability. Based on the data, most of the students were actively engaged in teaching and learning process and they understood the meaning of the tasks, it made them easy to do the tasks. It could be seen from the students’ participation and the score of their tasks in the cycle 1 and cycle 2.