Abstract: Different with the traditional dry style containment design without external cooling,the PCCS design increased the temperature difference between the wall and the containment atmosphere significantly,and also the absolute temperature of the containment surfaces will be lower,affecting properties relevant in the condensation process.A research on the heat and mass transfer model has been done in this paper,especially the improvement on the condensation and evaporation model in the presence of noncondensable gases.Firstly,the Peterson’s diffusion layer model was proved to equivalent to the stagnant film model adopted by CONTAIN code using the Clausius-Clapeyron equation,then a factor which can be used to stagnant film model was derived from the comparison between the Y.Liao’s generalized diffusion layer model and the Peterson’s diffusion layer model.Finally,the model in CONTAIN code used to compute the condensation and evaporation mass flux was modified using the factor,and the Wisconsin condensation tests and Westinghouse film evaporation on heated plate tests were simulated which had proved the improved model can predict more closer value of the heat and mass transfer coefficient to experimental value than original model.