The influence of relationship between wrap angle of impeller on performance of a pump was analyzed with the same main dimensions of centrifugal pumps unchanged. Blades were shaped using Hermite interpolation method. The wrap angle of impellers used in this investigation is 90°, 120°, 150°and 180° respectively. The result of numerical simulation indicates that the wrap angle changes the head and power characteristics by changing the relative velocity angle in impeller outlet. The effect of the different wrap angles is similar to that of the different impeller outlet blade angles. The bigger the wrap angle is, the smaller the separation and vortex in impeller passages are. With the wrap angle increases, the streamlines and blade profiles are getting similar, but the friction loss in impeller passages is getting large. So there exists an optimum wrap angle that corresponds to the highest efficiency of a centrifugal pump.