The wind energy pump system is a new green energy technology. The wide high efficiency region of pump is of great significance for energy conservation of wind power pumping system. In this study, factorial experiment design (FED) and computational fluid dynamics (CFD) are employed to optimize the hydraulic design of wind energy centrifugal pump (WECP). The blade outlet width b2, blade outlet angle β2, and blade wrap angle ψ are chosen as factors of FED. The effect of the factors on the efficiency under the conditions of 0.6Qdes, 0.8Qdes, 1.0Qdes, and 1.4Qdes is systematically analyzed. The matching feature of various volute tongue angle with the optimized impeller is also investigated numerically and experimentally. After the optimization, the pump head changes smoothly during full range of flow condition and the high efficiency region is effectively improved. The weighted average efficiency of four conditions increases by 2.55%, which broadens the high efficiency region of WECP globally. Besides, the highest efficiency point moves towards the large flow conditions. The research results provide references for expanding the efficient operation region of WECP.