The speed sensorless control method, which is based on the extended electromotive force (EEMF) model of interior permanent magnet synchronous motor, is difficult to make into use and its parameter dependence is strong. So a method to simplify the EEMF model was proposed and a simplified full order state and sliding mode observer (FOSSMO) was designed in order to achieve sensorless control. In addition, a simplified stator flux and electromagnetic torque observation method was presented. Then, torque closed-loop control system without speed sensor is established. The simulation and experimental research show that the proposed sensorless stator flux and electromagnetic torque observation method is independent of all the inductance and permanent magnet flux linkage parameters and the transient characteristic of the sensorless torque closed-loop control system is good.