When In-Vessel Retention (IVR) strategy is implemented under severe accident, due to the high temperature of the melt in the lower head, the Reactor Pressure Vessel (RPV) will bear relatively large internal and external temperature differences, pressure differences and thermal stresses, and thus will deform. This will lead to the reduction in the area of the natural circulation flow channel between the RPV and thermal insulation layer, which may have an impact on the characteristics of natural circulation and the Critical Heat Flux (CHF) on the outer wall of the RPV. In this paper, RPV deformation influence on ERVC flow channel natural circulation and CHF experiment was performed in REVECT-II facility. The influence of RPV deformation on the flow channel was simulated by adjusting the structure of the flow channel baffles, and CHF experiment was carried out for the azimuth positions with relatively larger RPV deformation amount. The research results show that, at the basic heating power level, the influence of RPV deformation on the natural circulation flow rate is not obvious. After deformation, the CHF at different azimuth increases or decreases, and the maximum variation amplitude is within 5%. Judging from the CHF values, the safety margin of the cases studied in this paper is more than 30%.