In order to improve the performance of vale controlled asymmetric system, a hybrid control method combining feedback linearization and sliding mode variable structure control was proposed. A nonlinear model of vale controlled asymmetric position servo system model was translated into linear model by using feedback linearization method. Based on the linear model, a sidling mode control algorithm was designed which can be used in the nonlinear model by inverse linear transformation. Last, to compare the proposed hybrid method to the traditional PID method, the numerical simulation was carried out. The comparison shows that robust feedback linearization can effectively restrain the outside disturbance and improve hydraulic position on tracking accuracy. 