The cause for the generation of prerotation and recirculation in the suction chamber was analyzed and the two-sided effect of prerotation on the hydraulic performance in centrifugal pump was pointed out. The effective solution was baffles built in suction chamber. With different physical parameters and placement of the baffles in suction chamber, CFD numerical simulation was applied to predict the performance variation trend of centrifugal pump. According to the performance curve and the flow state in the chamber, the optimum baffle came out: the radial length is D0 /4 (inlet diameter), and the 3/4 length of chamber is the value of axial length for the baffle. And, two baffles should be put closed by the impeller. The prototype was designed for hydraulic modeling test. The result indicated that the performance of the new model is superior to the original one. The values of head and efficiency rose by 0.8m and 1.7% at the design condition, relatively. Fluent numerical simulation with high accuracy could be applied in structural optimal design of centrifugal pump. 