For sensorless control of the permanent magnet synchronous motor(PMSM), the estimated accuracy of the angular velocity and position angle will directly affect the control performance of PMSM. As state observer has the advantages of simple structure and low noise, this paper proposes a novel sensorless control method on the basis of the current closed-loop state observer. The method is based on mathematic deducing of relationship between the electromagnetic torque and the angular velocity in accordance with the PMSM’s mathematic model and the control theory. A system simulation model and experiment platform are set up, simulation and experiment results verify the effectiveness and validity of the proposed sensorless control method.