The friction and wear of the piston directly affects the starting torque,working efficiency and service life of the inner curve hydraulic motor.The surface treatment technology can improve the wear resistance of the piston surface,but the existing coating process has the problems of wear and easy peeling.In order to explore the influence of different surface treatments on the friction and wear resistance of the piston,three surface treatment methods of MoS2 coating,DLC coating and QPQ salt bath composite treatment were compared and analyzed.Through the assembly test of the motor,the process flow that is most suitable for the surface strengthening of the internal curve hydraulic motor piston was obtained,and the wear-resistant surface strengthening process method of inner curve hydraulic motor piston was established.The test results show that the combined treatment with QPQ salt bath has the best wear resistance,and the working pressure of the motor can be increased to 25 MPa,which effectively improves the friction and wear problem of the motor roller and piston pair.