Abstract: The motor direct-drive actuator is based on servo control technology, and the high-voltage switch is directly driven by the motor, which has the advantages of simple transmission structure and customized motion characteristics. However, the traditional PI controller has limited robustness and dynamic response performance when dealing with complex load disturbances. To address the problem of decreasing robustness of the speed control system due to load perturbation in the motor direct-drive actuator mechanism, the H∞ hybrid sensitivity design method is introduced and a new parameter design scheme of speed PI controller is proposed, which is based on the selection of the uncertainty weight function and the performance weight function of the permanent magnet synchronous motor(PMSM) speed control system, and combines with the H∞ hybrid sensitivity design theory, to solve the speed PI controller parameter which meets robustness and dynamic performance requirements of the speed PI controller parameters. Simulation and experimental verification show that this method has significant improvement in speed regulation performance, is more robust than the traditional controller parameter frequency domain design method, and is suitable for direct-drive actuator systems in industrial applications.