Abstract: In the infinite speed system of surface permanent magnet synchronous motor, to further improve the speed in constant power flux-weakening operating region, it is necessary to switch the control strategy to make it work in the deep flux-weakening operating region. Whether the switching point is accurate or not directly affects the control stability. First, the out-of-control analysis is carried out, then the optimal switching point is identified between the constant power flux-weakening operating region and deep flux-weakening operating region. Besides, according to the optimal current trajectory, a hybrid flux-weakening control strategy based on lead angle combined with MTPV is proposed to realize the simultaneous control of d, q- axis current, and the control algorithm is simple. Finally, the effectiveness of the control strategy is verified by simulation and experiment.