Abstract: Based on the analysis of CPR1000 charging pump hydraulic performance test, it is found that the large inlet area of the diversion body is the main reason for the high shaft power. Every piece of steel plate was welded to the inlet tongue respectively to improve the hydraulic performance of the charging pump. Firstly, with the help of Ansys CFX, the flow field inside the charging pump of the modified scheme was numerically simulated and compared with the measured hydraulic performance data before the scheme modification. Then the hydraulic performance of the charging pump was tested and verified. The results show that the shaft power of the charging pump is controlled below 650 kW, meeting the requirements of the evaluation test program and technical specification, and the safety and reliability of the charging pump is improved.