Abstract: Centrifugal pump is one typical application of fluid mechanics theory. Many textbooks for fluid mechanics include centrifugal pump as an important chapter. When conveying a single medium, the flow in the pump is the compound movement of circular motion and relative motion. When conveying the solid-liquid two-phase, there is also a velocity difference between the two phases, hence the internal flow is very complicated. If these complex fluid movements can be visualized to demonstrate flow pattern, it will be a very good supplement to theoretical teaching, which will strengthen students understanding and consolidate classroom knowledge. For better visualize the internal flow, the pump and pipelines are made of transparent material, hence the impeller and volute area can be viewed without obstruction. Using particle image velocimetry (PIV) technology to capture the internal flow, a single medium or two-phase medium flow can be observed in the impeller observation experiment from a macroscopic perspective, velocity field of single medium and the relative velocity of two-phase medium can be measured locally.