Based on the vector control of permanent magnet synchronous motor (PMSM), an optimized fluxweakening control method of PMSM was proposed. The interior permanent magnet synchronous motor (IPMSM) had a relatively wider speed adjustment range than the surfacemount PMSM. Taking IPMSM applied as the object, we carried out simulation and optimization of the fluxweakening speed control. PMSM used the maximumtorqueperampere constanttorque control below the base speed to reduce the motor loss and improve the efficiency of the inverter. Above the base speed, PMSM adopted constantpower speed control. The combination of crossaxis current control and directaxis current control in the fluxweakening control method could improve the PMSM power factor and extend the speed adjustment range. Aiming at the fluctuation of the weak ring speed, the fuzzy selftuning PI control method was proposed based the traditional PI control. The simulation model was established in MATLAB/Simulink, and the feasibility of the control method was verified.