Grammatical aspect became an important aspect in learning process that have to be known by students. It was quite difficult to engage all of the students in the learning process, especially in teaching grammar for senior High School students. Based on this reality, the writer proposes to use “The Mistake Buster” technique to solve the problem. Besides, it could also give the sense of accomplishment to the students due to the opportunity to identify and correct the possible mistakes themselves instead of the teacher telling them what the mistakes are. The researcher used Classroom Action Research (CAR) for this study. There are 27 students as the object of this study, This study uses 2 pieces of instruments, namely observations of student activity in class and grammar tests to determine students' grammar scores. The findings of this study showed that Based on student data, it was known that there has been an increase of 92,5%. The value obtained by students has exceeded the minimum completeness criteria (KKM) that have been determined. Based on the previous description, this can be seen from the learning outcomes which have increased by 92,5%. It was concluded that learning with the Mistake Buster Technique can improve the learning outcomes of the Recount Text theme in class X MA Ma'arif An-Nur Winongan. Mistake Buster Technique was suggested to use was strategy for teacher as an appropriate strategy in teaching student’s grammar and for further researchers, the Mistake Buster Technique can be used for experimental research to improve English in improving language mastery, especially in the simple past tense. Keywords: Mistake Buster, Grammatical Mastery, Learning Technique