Abstract: External reactor vessel cooling (ERVC) strategy is proposed to be adopted as a key issue of in-vessel retention (IVR) which is applied in AP1000 as an important method to avoid the consequences of severe accidents. Most researches concerning about the critical heat flux (CHF) of ERVC are based on experiments. This paper dedicated to explore a way with computational fluid dynamics (CFD) method to solve where CHF happens and predict the value. And Eulerian multiphase CFD models were developed to resolve wall boiling and CHF. The numerical results for CHF of ERVC were validated against existing experimental data in this paper. The calculation results indicate that CHF will not occur, which agrees well with experimental results, and it is feasible to analyze ERVC by CFD.