In this paper, in order to investigate the effects of blade number on the characteristics of the centrifugal pump, a typical centrifugal pump is chosen as research model. The flow fields of model pump were simulated in non-cavitation and cavitation condition. The impellers with different blade number were made by using rapid prototyping. The characteristics of model pumps were tested in an open rig. The predicted results of head, efficiency and required net positive suction head(NPSHR) were compared with the experiment data. Also, the effect of blade number on the inner flow field and characteristics of model pumps were analyzed.