Abstract:To improve teaching forms and methods and to improve consistently the pertinence and effectiveness of ideological and political theory course in university are the basic tasks of new round teaching reform of ideological and political theory course. But the large classes that existed widely in China's universities after its mass expansion have become the bottleneck of taskperforming. For solving this problem, it is insufficient to optimize the large class teaching, and it is necessary to reduce the size of large class. Under current conditions, the medium class teaching is a feasible alternative. In this paper, a comparative study on large class and medium class of ideological and political theory course in university has been made. By analyzing the respective characteristics of large class and medium class, and revealing the different effects of these two teaching forms to the teaching effect, the necessity of medium class teaching is presented,and some basic problems about how to implement medium class teaching are investigated. From this study we have drawn the following conclusion: by implementing medium class teaching, the pertinence and effectiveness of ideological and political theory course in university can be greatly improved, and to change the class size from large class teaching to medium class teaching is concerned with not only the number of students, but also corresponding changes of the teaching forms and methods, teaching resources, teacher management system, and so on.