With the development of science and technology, national security and social life can not be separated from electricity every moment, and the safety of power grid is becoming more and more important. At present, the research on relay protection model in dynamic simulation of power system in China is still in the primary stage. Because the research is not deep enough, the control law of relay protection elements can not be well grasped. The failure can not be handled well. Therefore, in order to ensure the safe operation of the power system, we must first strengthen the grid structure of the power system, improve the elasticity coefficient, distribute the reserve capacity reasonably, strengthen the adjustment ability of the tie line between the major power grids, and improve the stable reserve of the power grid. In order to improve the authenticity and reliability of dynamic simulation, it is necessary to establish a set of relay protection models, which should be consistent with the actual relay protection. In this way, the stability problem in power system can be analyzed accurately to improve the reliability of power system. The relay protection model established in this paper reduces the complexity of modeling and can reflect the dynamic characteristics of power system after interference. It is of great significance to the analysis and research of power system.