Because the gear system is a complex nonlinear system, it is difficult to establish a complete nonlinear dynamic model of the gear system. Therefore, we need to simplify the gear pair and only consider the meshing relationship between the center gear and the planetary gear. At the same time, considering that the meshing stiffness and centroid of the gear will change and deviate with the degree of broken teeth, the dynamic model only considers the vertical displacement of the gear, and does not consider the angular displacement, so the dynamic model can be established.