This paper expounds the characteristics of Simulink in MATLAB, and its great role in power system simulation. It illustrates the basic methods and steps of Simulink simulation. In this paper, after the analysis on the basic equations of synchronous generator and the theory of three-phase short circuit, Simulink is used to simulate the three-phase short circuit of the synchronous motor under the condition of no-load. Compared with the theory, the effectiveness of Simulink simulation is explained.