The surface permanent magnet synchronous motor was taken as object, the traditional DC bus voltage feedback flux weakening control algorithm principle and implement method were studied. In order to solve the problems of in the flux weakening region of PMSM, the oscillation of speed in high speed state, and not good at load ability, an improved adaptive flux weakening control method was proposed. The limited maximum value of the current component i_d was calculated by the current component i_q through feed-forward control based on PI control, and was used as the given value. The method can increase the speed of system response, and get the accurate i_d much more quickly, achieve rapid adaptive control. The simulation and experiments based on Matlab/Simulink and dSPACE showed that the improved adaptive flux weakening control strategy can effectively reduce the oscillation of speed in steady state, and improve the load ability of PMSM in high speed.