A new type of integrated fan using hydraulic servo valve to control hydraulic cylinder was designed. The main structure parameters, such as damper orifice diameter and the area gradient of servo valve port were optimized, and the influence of rapidity, accuracy, stability and dynamic stiffness of the system was analyzed. The mathematical model of the three-way valve control asymmetrical hydraulic cylinder system was established, which was investigated for system simulation. The research results provide some theoretical foundation for the experimental test of fan air volume adjusting servo mechanism and finalizing the design.