In order to understand the flow pattern of salt-out particles in a vortex pump, PIV was adopted to measure the particle flow field. The quasi three dimensions velocity field of the particles was obtained. The particle flow characteristics were primarily known under several running conditions. It is indicated that velocity distributions are obviously different on various axial sections in the impeller. The forced and free vortexes were both existed in the vaneless volute. When the pump flow rate increased, particle relative flow velocity increased at the impeller inlet, as well as the relative flow angle at the impeller outlet. Near the small radius area of vaneless volute, radial velocity component increased with the flow rate changed. There is also portrait vortex of particle flow, and the vortex center is located around the centre of impeller flow passage. It is almost no change with the flow rate.