Abstract. This paper presents a method of improving the position response speed of the servo system based on electromechanical actuator position servo system. In this paper, a novel decouple technique is derived from PMSM decouple state equation, separating direct axis current from quadrature axis current ulteriorly, and the impact of EMF in high dynamic conditions is overcome. Based on analysing the principle of slide mode variable structure (SMVS), the boundary conditions of SMVS control and equivalent control strategy, the method of applying SMVS in the servo speed system has been put up, and the SMVS controller for the speed-loop has been built. The system uses feed-forward control to compensate the position deviation of PMSM in steering engine. Feed-forward transfer function is analysed and feed-forward controller is established to ensure the performance of electromechanical actuator applied in missile.