In order to find out the effects of splitter blades on the performance of pump as turbine, a pump as turbine and an open pump as turbine test rig were built. Research results showed that the addition of splitter blades could improve its efficiency, increase its flow rate at the best efficiency point and decrease its required pressure head. Internal flow field analysis showed that the flow field was improved and the area and intensity of vortex region was decreased with the increase of splitter blades. Power loss distribution analysis within pump as turbine showed that power loss within impeller took up the majority of the total power loss. The power loss within impeller was decreased when splitter blades were added to the impeller. With the increase of blade number, the interaction of impeller and volute was enhanced, so the power loss within volute was increased.