<p>Main shaft seal leakage is a typical challenge affecting the operation of hydraulic turbine. The incorporation of a pump plate device can enhance main shaft seal performance. To investigate the working characteristics and improvement potential of the pump plate device for Francis turbine main shaft seals, this study employs computational fluid dynamics (CFD) technology, utilizing the Hongshanzui hydropower station (Xinjiang, China) as a case study. Firstly, separately improve the angle of the pump blades and the height of the pump cover. Secondly, jointly improve the pump blades and the pump cover. Finally, select the optimal structure. The results show that the addition of a pump plate device significantly impacts the flow of leaked water; changing the height of the pump cover is more advantageous than changing the angle of the pump blades; the installation of the pump cover should avoid the most unfavorable height ratio of 0.1359; increasing the height of the pump cover can reduce water leakage, improve the efficiency of the pump plate device, and increase the drainage capacity of the top cover; using a pump plate device with radial pump blades and a pump cover height ratio of 0.1902 as the optimal improved structure can increase the pressure at the labyrinth seal outlet by 17.8%, the pressure difference between the inlet and outlet of the pump plate device by 11.7%, and the pressure at the top cover drainage hole outlet by 14.5%. This study provides valuable insights for the design and retrofitting of Francis turbine main shaft seals.</p>