Abstract: The pumped storage power station constructed on a reservoir in a sediment-rich river basin is susceptible to damage caused by the abrasive effects of sediment particles on the surfaces of the primary flow components. Utilizing the standard k-ε turbulence model, the particle motion equation, and the McLaury wear model, this study employs the Euler-Lagrange approach to numerically simulate the sand-water flow characteristics and predict wear in the pump turbine under transitional operating conditions. The findings reveal that the internal flow field of the pump turbine undergoes substantial alterations in the hump characteristic operating region, marked by the presence of prominent vortex structures in the non-bladed zones and within blade passages. A reduction in sand-water flow leads to a significant increase in the spatial extent of regions with high turbulent energy fluctuation(TEF>1800 s–1), expanding from less than 5% to over 30%. The direct entropy production rate and indirect entropy production rate increase by 22.4% and 34.6%, respectively. The flow instability characteristics of the blade passage vortex and the unstable flow lead to disorder in the particle motion trajectory, and the complex coupling between the particles and the vortex intensifies the uncertainty of the particle migration path. The Reynolds number of the particles inside the runner and the guide vane increases by 3-5 times under the three operating conditions. The average differences in particle and water flow velocities under low-flow conditions are about 0.7 m/s, 6.4 m/s, and 3.3 m/s, respectively. The particle momentum enrichment area is mainly distributed in channels 2# to 4# and the outlet of the runner flow channel under low-flow conditions, and the area of the high-momentum region inside the runner exceeds 30%. The maximum wear rates on the suction side and pressure side of the runner blade are 8.3×10–8 kg/(m2·s) and 5.6×10–8 kg/(m2·s), respectively. The average wear rate difference of different blades reaches 1 to 3 times. The wear distribution on the surface of the movable guide vane is relatively small, and the enrichment phenomenon of particles by the blade passage vortex has a significant impact, whereas the influence of the vortex in the non-blade area flow channel on the particles is weak.