Students in eleven grade had a different style for answering the physics problems. One of the sub-chapter in physics was Boyle-Gay Lussac’s Law. It included in Kinetic Theory of Gases. This research aimed to (1) identify student’s answer in resolving Boyle-Gay Lussac’s Law problem, and (2) know the kind of student’s answer into five categories. The research was qualitative research. Based on the approach and purpose, this research was a descriptive research to describe or explain the existed thing. It was taken place at MAN Yogyakarta I in semester two on eleven grade. The obtained datas were collected by test sheet that contained of essay form. The respondents were all of the students in XII MIA 3. The data was analyzed by quantitative analysis using rubric of scoring in essay test and qualitative analysis using Miles and Huberman model. The results such as (1) student’s answer was identified into five categories, and (2) knowing the categories into percentage which doing in reasonable way 45%, unfinished answer 32%, abandoning the unit 9%, undone answer 9%, also wrong process and answer 5%.