Abstract: Loss of coolant accident (LOCA) is a typical design basic accident (DBA) for pressurized water reactors (PWR). The containment thermal response process, especially containment peak pressure (CPP), will directly affect the structure integrity of the containment. The deterministic realistic methodology (DRM) was applied to analyze LOCA mass and energy release and containment thermal response for HPR1000 nuclear power plant (NPP). Sensitivity analysis and statistical calculation were made for the key parameters, and the DRM penalty model was established. The results show that the calculated value of DRM penalty model is always higher than the statistically calculated values with 95% confidence level and 95% probability. The study proves the conservatism of DRM penalty model and also demonstrates the applicability of DRM for LOCA mass and energy release and containment thermal response analysis for HPR1000 NPP.