Motion of tracer particles in the centrifugal pump was calculated by discrete phase model. In this model, the fluid field of the centrifugal pump was solved by the two-equation RNG k—ε turbulence model. The pump performance curves were simulated to check the calculation accuracy by comparing with the experimental performance curves. Based on the result of the flow field, the tracks of tracer particles with different densities and diameters in various conditions were achieved by using Lagrange method. Through comparing particle trajectory with fluid streamline and analyzing the particle speed changed in the relationship with the spatial scale, the particles tracking characteristics were studied. Numerical simulation results showed that tracking characteristics of different densities, particles were significantly different when their diameters were greater than 50μm. While diameters were less than 20μm, densities were very low impact on the following performance. It was very important when the particle density was equal to the density of fluid. In the channel with unstable flow such as the vortex flow, the particle trajectory line was closed to the fluid flow line when the tracer particle with smaller diameters and the density was the same with the fluid density. Changing with spatial scale, the particle’s speed was closed to the fluid velocity when the particle’s diameter was under 20μm. Finally, taking the particle scattering characteristics into account, it was recommended that 20μm polystyrene should be chosen as tracer particles for this centrifugal pump.