In order to study the influence of tooth surface friction on the bifurcation characteristics of planetary gear system, the torsional vibration model of planetary gear system is established by considering the nonlinear factors such as friction, time-varying meshing stiffness, backlash and comprehensive error. Runge-Kutta numerical method is used to solve the problem, and the bifurcation behavior of the system and the influence of tooth surface friction on the bifurcation characteristics of the system are analyzed by combining the nonlinear analysis method. The numerical simulation shows that the planetary gear system shows Hopf bifurcation, jump shock, doubling bifurcation and inverse doubling bifurcation. The influence of tooth surface friction on the bifurcation behavior of the system in the low frequency region is small, and the bifurcation behavior of the system is basically unchanged. The influence of tooth surface friction on the bifurcation behavior of the system in the high frequency region is large, and the bifurcation behavior of the system becomes fuzzy, and enters the chaotic motion in advance. With the increase of friction coefficient, the periodic motion of the system with the change of excitation frequency is restrained more obviously, and the chaos degree of the system is also increased obviously.