Abstract: Taking a once-through steam generator designed by Babcock & Wilcox as the study object, a graphical model was designed, based on the basic module of supporting platform APROS. Based on the simulation with the different two-phase flow calculation model, after comparative analysis, a six-equation model was selected for calculation. The simulation results from different working conditions are compared with the results of empirical formula for pressure and heat transfer calculation, and the fluid pressure and heat transfer efficiency in the model are modified. Then the steady-state and dynamic simulation results under the set working conditions are compared with the experimental data published abroad to verify the accuracy of the model.