The invention discloses a permanent magnet linear synchronous motor slip form control system based on a linear expansion state observer, and belongs to the technical field of linear motor control. The system comprises the following steps that: firstly, establishing the dynamic equation of a permanent magnet linear synchronous motor on a two-phase synchronous rotation orthogonal coordinate system; secondly, simplifying the dynamic equation into a special two-order integral series type mathematical model; thirdly, designing the linear expansion state observer to obtain a disturbance estimated value, and considering the estimated value in the design of a slip form control law to eliminate a chattering phenomenon; and finally, applying a Lyapunov stability theory to analyze the stability of the system. The system has the most important characteristics that the state and the disturbance of the system can be accurately estimated by the linear expansion state observer. In addition, the control system is high in robustness, and a given displacement signal can be accurately tracked. In addition, the chattering phenomenon of slip form control can be greatly improved so as to be suitable for designing the permanent magnet linear synchronous motor servo control system.