Phase Doppler particle anemometer (PDPA) was used to measure the velocity field of liquid-solid two-phase flow under the optimum operating condition of a vortex pump. Radial velocity and axial velocity models were adopted to obtain 3-D velocity information of one point according to the characteristics of inner flow field in vortex pump. Velocity and corresponding fluctuating velocity of each phase in volute and impeller were gained by separating particle diameters method. Motion rules of two-phase in the pump were revealed by the analysis on distribution curves of circumferential velocity, axial velocity and radial velocity. It is proposed that velocity of solid phase is basically larger than that of liquid phase in impeller and so on. 