An adaptive PID controller based on disturbance observer is designed to deal with the problem of speed tracking accuracy of permanent magnet synchronous linear motor (PMSLM). A nonlinear disturbance observer is designed for the linear motor model based on vector control. Based on Lyapunov function, the overload compensation controller is designed and the projection adaptive law is updated on line. These make the PID control law follow the feedback control law. Experimental results show that the control strategy has better dynamic performance and robustness.