Advanced flow measurement equipment PIV (particle image velocimetry) was adopted to measure the internal salt-out flow in an innovated centrifugal pump. The synchronization problem during measurement was guaranteed by using shaft encoder and frequency dividing circuit. Based on the platform of Visual C++ 6.0, the special image processing kit was developed to differentiate solid and liquid particles in the flow images. Investigation of the two-phase velocity fields prove that the crystal particles changes the relative liquid velocity distribution, and the outlet liquid velocity decreases compared with that under single phase condition. It is also concluded that the crystal particles have the tendency of moving towards the pressure side in the middle of the channel. The characteristics of salt-out flow in the pump were obtained, and some guiding advices were presented to prevent salt-out in pump impeller.