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 the failure of the motor curve guide rail under the heavy-duty condition of low-speed and high-torque internal curve hydraulic motor. An optimization method for medium-frequency quenching process of curved rail surface heat treatment is proposed. On the basis of conventional methods, the processing principle of curve grinding machine profiling is applied, that is, computer numerical control (CNC) profiling is used for heat treatment. And the performance parameters of curved guide rail after conventional quenching and optimized CNC profiling quenching treatment are 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. In terms of hardness, it is increased by 3~5 HRC; In terms of hardening layer depth, it is increased by 1.5~3.5 mm This optimization method can guide the application of curved hydraulic motor curved guides in heavy duty conditions.