Aiming at the problem of tracking performance degradation of permanent magnet direct-drive wind turbine system during maximum power tracking due to internal parameter changes and external disturbances, a model free fixed-time integral sliding mode control (MFFTISMC) method is proposed. Firstly, a novel ultra-local model of permanent magnet synchronous motor speed ring is constructed. Based on this model, a model free fixed-time integral sliding mode controller is designed in combination with the fixed-time theory to ensure the convergence of the system state in fixed time, and the convergence of the controller is proved using the Lyapunov function. Meanwhile, in order to improve the anti-interference ability and tracking performance of the system, an extended disturbance observer (EDO) is designed to estimate the uncertain disturbances in the novel ultra-local model online and compensate them to the controller by feed-forward compensation.Finally, through simulation and comparison with other control strategies, it is verified that the method is characterized by fast response speed and strong disturbance resistance, and is able to quickly realize the maximum power tracking under the sudden change of wind speed.