Abstract: The operational characteristics of passive residual heat removal system on the rolling roof were investigated experimentally. On the basis of RELAP5/MOD3.2 code, the two-fluid model was substituted with drift flux model. This code was improved by modifying the mixture momentum equation and condensation heat transfer model. The passive residual heat removal system under rolling motion was simulated by the advanced code, and it was consistent with experiment results. The discrepancy between calculation and experiment results was less than 10%. The advanced condensation heat transfer model can also be used to calculate the condensation heat transfer coefficient with droplet carryover precisely. In the experiments, the fluctuation of condensate temperature and steam pressure was very limited.