Abstarct: Since importance of pitch control in power control of wind turbines, spatially in third operation region with constant Rotational speed of the turbine, it is needed to choose a suitable controller for pitch actuator, separately from main turbine control loop. In this research Hydraulic actuator is considered as the pitch actuator of a 2 MW wind turbine. The purpose is design of a high-performance controller, considering the control requirements and special constraints which is applied on the actuator by turbine. Due to nonlinear actuator model and presence of some uncertainties in its mechanical parameters and wind speed disturbances, we use a robust nonlinear controller. For this purpose, a novel sliding mode control (SMC) is uses. The discrepancy of this controller and conventional SM controllers is utilizing an adaptive switching control low. In this method, the magnitude of switching gain is determined according to amount of instance error with a simple function. For better evaluation For better evaluation, the new sliding mode controller results are compared with the controller using the feedback linearization method. Finally, simulation results show robustness of the control system against wide range of uncertainties. Also, the desired performance of the control system is confirmed by types of comparitions and validations.