A five-bladed centrifugal pump impeller with five splitters was designed for the experiment. Detailed 2D-PIV measurements of flow fields about three different fluxes inside the same rotating blade-to-blade passage have been successfully performed in conjunction with the overall pump performance measured separately. The complex internal flow patterns were acquired and the relative velocity varying law near the suction surfaces and pressure surfaces of long blades and the operation sides and opposite sides of short blades were also revealed. Blade-to-blade distributions of the relative velocity about three fluxes were obtained at different radial stations.