The conventional inductor medium frequency quenching method will lead to uneven hardness and depth of the inner surface hardening layer of the curved guide rail,and it is easy to cause failure of the motor curved guide rail of low-speed and high-torque internal curve hydraulic motor under heavy-duty condition.An optimization method for medium-frequency quenching process of curved rail surface heat treatment was proposed.On the basis of conventional methods,the processing principle of curve grinding machine profiling was applied,that was,computer numerical control profiling was used for heat treatment.And the performance parameters of curved guide rail after conventional quenching and optimized CNC profiling quenching treatment were tested respectively.Through analysis and comparison,it can be seen that the surface hardness of the curved guide rail obtained by the optimized CNC profiling quenching is higher than that of the conventional quenching method,and the depth uniformity of the curved guide rail hardening layer is better.The hardness increases by 3HRC to 5HRC,the hardening layer depth increases by 1.5 mm to 3.5 mm.The motor with the curved guide rail produced by the new process has been put into use,and no quality question about the curved guide rail has been fedback.