Background: Pressurized water Reactor Pressure Vessel（RPV） sealing capability is one of the key factors to ensure the safety operation of nuclear power plants.Purpose: In order to explore the numerical simulation technology of the RPV sealing behaviors.Methods: In this paper

the 3-D thermal elastoplastic finite model is established

which based on the CPR1000 project.Results: The load and its combination of equipment during operation are considered

then the separation of RPV upper and lower flanges

radial slip and bolt loads etc.are also obtained.Conclusions: The results show the 3-D thermal elastoplastic finite model can simulate the sealing performance of the structure.