Abstract: Using the finite element method, a model was established for the persistent leakage phenomenon occurring during load variation at the split-plane end of the high-pressure cylinder in a Russian-made nuclear power steam turbine, the influence of factors such as load level, bolt preload, and external shaft gland insulation on the leakage was significantly researched. Firstly, a finite element model of the high-pressure cylinder end was developed to analyse the impact of load level variations on the steam supply parameters of the shaft glands, and subsequently, the variation rule of the contact pressure at the split-plane end of the high-pressure cylinder under different loads was discussed. Secondly, the influence of bolt preload on the distribution of contact pressure was investigated. Finally, based on research findings, a solution involving external pressurized sealing was proposed, and a simulation body and sealing fixture for the end of the high-pressure cylinder were designed. Results show that bolt preload has a significant local impact on the contact pressure but has a relatively minor direct impact on the leakage area, while the external shaft gland insulation can improve the end contact condition to a certain extent. When the gap between the sealing fixture and the cylinder wall is less than 0.2 mm, the internal pressure within the simulation body of cylinder can be effectively maintained. While field implementation effects can further validate this conclusion.