With the development of the city sewage treatment, the request of the specific speed of axial flow pump has been higher and higher. At present China is lack of the system theory and method to design axial flow pump above 1400 specific speed. Selection methods of design parameters depend on experience. This paper used the improved lifting method to design axial flow pump. Optimize design of axial flow pump from cascade solidity, blade number, ratio hub and the airfoil of impeller. The feasibility of such optimize methods had been validated from theoretical analysis. Put forward new selection methods of design parameters. Design an impeller model. The rated condition of flow rate is 3000 m3/h and the rated condition of lift is 1 m. A useful reference of axial flow pump design, improvement and optimization was obtained.