For the sensorless control system of permanent magnet synchronous wind power generation, this paper proposes a second-order integral sliding mode variable structure model reference adaptive observer (SOI-MRASO). Firstly, the reference model and adjustable model are designed according to the mathematical model of permanent magnet synchronous generator (PMSG); secondly, the output error between the two models is used to construct the integral sliding mode surface, and the integral sliding mode controller (ISMC) is designed to replace the PI controller in MRASO to improve the robustness of the system. Then the second-order sliding mode control law (SOSMRL) is introduced to reach the purpose of suppressing the sliding mode jitter and improving the control accuracy of the system. Finally, the effectiveness of the proposed strategy is verified by simulation.