Abstract: In order to achieve better understanding of reflood phenomenon and make improvement on the mainstream system code,this paper use RELAP5/MOD3.2 code to simulate the FEBA（Flooding Experiments with Blocked Arrays） facility from Germany.firstly,the calculation is compared with the experiment data.results show that both the peak cladding temperature and the bundle quenched time are under predicted.Then sensitivity analysis is done to the important physical model parameters related to the reflood phenomenon.The results prove that the interfacial friction of bubbles and droplets,heat coefficient between gas and interface of dispersed flow,wall to liquid drag coefficient,heat transfer of film boiling flow regime and the minimum droplet diameter are parameters with relatively large influence.More efforts should be made on the research of these parameters and models in the next step of work.