Abstract: In order to study the working characteristics and optimization feasibility of the upper crown runner pump of medium and high head Francis turbine,taking the No.3 turbine of Hongshanzui First Stage Power Station as an example,the existing runner pump and 11 structural optimization models are established,using CFD commercial software,based on The SST turbulence model carries out numerical simulations of runner pumps with different structures under 9 flow conditions.Taking the leakage flow characteristics of the upper crown channel,the vacuum degree of the main shaft seal and the working efficiency of the runner pump as the research indexes,the results show that the leakage flow characteristics of the upper crown channel depend on the structure type of the runner pump;reducing the"pump cover height ratio"of runner pump or inclining the pump blades has a significant effect on improving the vacuum degree of main shaft seal（the best structure can increase 66.9%）,and its working efficiency must be considered at the same time;under the rated working condition,the working efficiency of the runner pump is low,therefore it is recommended to set up appropriate drain holes on the upper crown of the runner to make up the flow and improve its efficiency;the power station can set the pump blades at an angle of 45°and the runner pump with pump cover height ratio H_P=0.0543 as the best improvement scheme.The study quantifies the structural parameters of the upper crown runner pump,which makes the conclusion universal,and provides a certain reference basis for adding runner pump at the top of the upper crown of medium and high head Francis turbine and its optimization.