Permanent magnet synchronous linear motor (PMLSM) has the characteristics of nonlinearity, coupling, load disturbance and time varying uncertainty. It is very difficult to achieve precise control by simple PID control. In view of the shortcomings of slow dynamic response and poor anti-interference ability of PID control of PMLSM, a control strategy of replacing PID controller with back-stepping controller is studied in this paper. In order to solve the problem of tracking error and reduce tracking performance, such as load force and thrust fluctuation in the permanent magnet synchronous linear motor drive system, this paper designs an extended state observer and feedback its observation to the design of the back-stepping controller. Therefore, the back-stepping control of permanent magnet linear synchronous motor based on the extended state observer has the advantages of fast speed, small overshoot and so on, and has strong robustness to the load disturbance.