Abstract: The In-Vessel corium Retention（IVR） strategy of Chinese 1000 MW class commercial pres-surized water reactor（CPR1000） is assessed by Risk-Oriented Accident Analysis Methodology（ROAAM）.Four representative severe accident scenarios are selected for the IVR assessment in this paper.According to four representative severe accident scenarios consequence calculated by the deterministic code combined with engineering judgment,the input probability distribution of the assessment is determined.Success probability of IVR from the viewpoint of thermal failure is then predicted using MOPOL code.MOPOL is a code devel-oped basing on the well known ROAAM frame and heat transfer model of corium.It is demonstrated that the success probability of IVR by Reactor Cavity Flooding in CPR1000 is potentially higher than 99%.Applica-tion of IVR strategy in CPR1000 is envisioned probable if a further more comprehensive risk-benefit evalua-tion conclusion is positive.