The purposes of this study were to investigate the perceptions of teachers and students on the implementation of the intensive course completion system in mathematics courses and to provide suggestions for the improvement of the system. Five high school mathematics teachers and 338 10th graders and 87 11th graders in 2 high schools located in Gyeonggi-do participated in this study. The results of this study indicated that the intensive course completion system is more appropriate to the subjects which require less time allotment or practical exercise than mathematics courses. For better implementation of the intensive course completion system in mathematics courses, first of all, enough time allotment for teaching and learning mathematics should be guaranteed. Otherwise, the system can make students feel more burden of learning due to increase in learning volume of mathematics courses.