Abstract: In view of the problem that the single friction model can′t accurately describe the robot joint friction, the dynamic equation of the robot joint servo system is established. Firstly, a mixed friction model is established based on the analysis of Static friction, Coulomb friction and Lorentzian friction model. Secondly, a mixed friction dynamic model of the robot joint is established to describe the friction problem inside the robot joint. The purpose is to improve the modeling and control accuracy of the robot. Finally, the proposed model is simulated by MATLAB/Simulink. Compared with other models, the results show that the accuracy of proposed model for robot joint is better.