Abstract: The PIV technique is a brandnew technique of measuring velocity. It started in the 1980s with the development of high speed photography and the image processing technique of computers. This paper deals with PIV applied to the study of solid particles velocity in the flow passage of centrifugal pumps. A set of software with Windows interface was developed to analyze the flow motion of such solid particles as rubber balls, walnut shellfractions and sand with different physical properties in the flow passage. The study shows that the density of solid particles has important effects on the relative trajectory of particles, the shape and size of solid particles mainly affect the amount of particles’ velocity. As to halfopentype impellers, the flow between blades and the pump cover being influenced by leakage, the relative velocity of particles is greater than that in the closedtype ones. So the reasons why the efficiency of opentype impellers is lower than that of closetype ones and opentype impellers are easy to wear are revealed. Results of the study are helpful for explaining abrasion in centrifugal pumps.