An integral fuzzy sliding mode control scheme is proposed for control objects with uncertain parameters and strong disturbances. The control approach introduces a new method of decomposition to overcome the strict constraint of model format in conventional sliding mode variable structure control, and add integral control to eliminate the assumption that the derivative of desired signal must be known. Fuzzy logic control is used to estimate the unknown uncertainties. The sign function of the switching surface function is replaced by a suitable saturate function to reduce the system chattering. The proposed method is applied to generator speed tracking control of a large-scale variable speed wind turbine. Simulation results indicate that the control approach is robust and improves tracking accuracy considerably.