In order to improve robustness of the permanent magnet linear synchronous motor servo systems, an active disturbance rejection backstepping controller was presented. The unmodeled dynamics and disturbance were defined as overall disturbance and viewed as a new system state. A LESO (linear extended state observer) was designed to estimate the velocity of the mover and the overall disturbance, and convergence proof and estimation error of the LESO were given. With the linearization via dynamic compensation, a backstepping controller was designed using the outputs from the LESO. The stability of the closedloop feedback control system was given considering the estimation error of LESO. The effectiveness of the proposed controller was verified in the experimental platform, which was made by Googol Company.