Abstract: It is very important to remain the integrity of reactor pressure vessel (RPV) in the core melt severe accident. The high temperature creep failure is the main failure mode for RPV in core melt severe accident. The altitude distributions of outer and inner wall temperatures are important inputs for structure analysis. In this work, the CFD method was used to carry out heat-solid-fluid coupled analysis of the corium in RPV, RPV wall and outer gas-water two-phase flow heat transfer. The temperature field, flow field, the fraction distribution of each phase in the coupled situation and the remaining thickness of the pressure vessel wall were obtained, providing the support for analyzing the RPV structure integrity in severe accident the reactor corium in-vessel retention (IVR).