The segmented structure of the long stator permanent magnet linear synchronous motor (LS-PMLSM) will cause the significant variation of the stator inductance, which will cause additional disturbance to the sensorless control when the mover is pasing through the stator segment. Aiming at this problem, this paper uses the disturbance observer to compensate the disturbance feed-forward, eliminates the fluctuation of the observed back EMF when the mover is over-segmented, and improves the accuracy of the velocity observation of the speed sensorless control of the permanent magnet linear synchronous motor. Finally, simulations results demonstrate the effectiveness of the method.