In traditional sliding mode observer (SMO) speed sensorless control method, a steadystate error would exist in position estimation when the speed of the motor fluctuated greatly. In order to eliminate the estimation error, a back electromotive force (backEMF) corrector was proposed based on the dqaxis current model of permanent magnet synchronous motor (PMSM). In this way, the position estimation error was kept at zero even under large speed fluctuation. Moreover, the proposed method was easy to implement and brought about small increment in calculation cost. Numerical simulations and experiments were carried out on a 1.5 kW PMSM. The results demonstrate that the proposed method can effectively estimate rotor position and the steadystate estimation error converges to zero.