Abstract: With the deepening of the reform of education and teaching in modern colleges and universities, a large number of problems arising in the basic course teaching cannot be fully solved only by teachers. The introduction of the teaching assistant system has become a necessary supplement to the teaching of basic courses in colleges and universities. Starting from the teaching practice of probability theory and mathematical statistics course, this paper introduces the design, implementation, and evaluation of the auxiliary teaching practice of the postgraduate assistants in detail. It shows that the teaching assistant system plays an important role in the foundation courses teaching process, as well as the catalyst of emotional interaction between teachers and students. Giving full attention to the work of postgraduate teaching assistant is an effective guarantee for improving the classroom teaching quality.