For the problem that the required net positive suction head (Nr) of a high-pressure flushing pump in a large trailing suction hopper dredger is too high under the light-load and large flow rate conditions,the impeller is optimized to reduce the critical Nr while maintaining the original hydraulic performance.In this study,numerical simulations of the cavitating flow in the high-pressure flush pump before and after optimization are carried out by CFD technology,and the key performance parameters as well as the cavitation flow field are compared for the large flow rate conditions.The results show that the critical net positive suction head point is reduced from 10.47 m to 6.03 m under the large flow rate flushing condition by enlarging the suction diameter and modifying the blade while the hydraulic performance in the four conditions is maintained to meet the desigh requirement,which means the cavitation performance of the high-pressure flushing pump has been effectively improved.