The flow fields in a rotating impeller, near the volute tongue of a centrifugal pump, were measured by the 2-D PIV technique. At the flow rate of Q/Qbep＝0.52, a counter clockwise recirculation flow existed on the blade pressure-side, when the blade was close to the volute tongue, a clockwise recirculation flow occurred on the blade suction-side. At the flow rate of Q/Qbep＝1.0, a jet/wake flow existed at the exit of the impeller. The results show that the effects of the volute tongue on the relative velocity distribution are more significant at the low flow rate condition than at the best efficiency point.