The goal of this study is to improve student’s vocational skills in chemistry, especially petroleum matter class XI Semester I. This research was done in two class, those are Class XI Science 2 and Class XI Science 3. This goal was achieved through project based learning model by making biodiesel as fuel alternative. Assessing student’s vocational skills was done by vocational skill test based on Guttman scale. The first test was done before the project based learning was started (pretest) and the second one was after the project based learning completed (posttest). The first observation indicated that all of students can not make biodiesel and it means their score of vocational skills was zero. All of students achieved both individual and clasical completeness in the posttest. Furthermore,the gain score of both class were 0,88 and 0,87.