A method is introduced to achieve position sensorless control and online stator resistance identification for PMSM in the full speed range. The high-frequency square wave injection method is utilized to accomplish position sensorless operation at zero and low speedwhile switching to the synchronous shaft sliding mode observer at medium and high speed. The stator resistance is closely related to winding temperature and control performanceand it can be calculated by Ohm′s law with the DC disturbance current injection and closed-loop control in the stationary two-phase coordinate system. The proposed method does not rely on other motor parametershas little impact on the system operation and is widely applicable. The simulation results show that the accuracy is ±5%which can be used to monitor the winding temperature and improve the performance of position sensorless control.