A new method for Flux Weakening (FW) of Surface Permanent Magnet (SPM) motors is proposed in this paper. This method is termed a dual inverter-fed drive system with winding switching which can significantly extend the field weakening speed range of SPM motors. As a particular design example, the proposed method can increase the maximum output power of a SPM motor by 73% without changing the battery rating, and can extend the constant power speed up to about 4 times the base speed without sacrificing the torque capacity at high speed. The stator winding arrangement which allows the motor operate in various speed operations is discusses in this paper. The simulation and analysis of the drive system with respect to a SPM motor is implemented, and the simulation results show the motor operates reliably and flexibly by the proposed method.