This paper designed a small course early warning system based on KNN algorithm, aimed at students haven’t finished the course of time can be completed by yourself some predict their courses by chance. In this paper, the basic principle of KNN algorithm is briefly introduced, and the course warning system is modified by Manhattan distance with added weights. This paper briefly describes the basic framework of this model and introduces the application of KNN algorithm in this model. Through a large number of basic experimental data to test the training, using figures to show, finally get the curriculum early warning system model, to achieve the effect of curriculum early warning.