Abstract: The effect of separator corrugated-plate water-film flow on the forming of secondary droplets was studied by numerical method. By analyzing the flow character of water film on separator corrugated plate, and using reasonable simplifying and hypothesis, water film physical model and mathematical model were developed. Using finite volume method, convection term was discretized with two-order upwind dif- ference algorithm, and diffusion term was discretized with central difference algorithm. ADI （Alternat- ing-Direction Implicit） solution was used. By numerical simulating movement of water film on separa- tor-corrugated plate, under main steam transverse sweep situation, the relations between the water film pa- rameters and wet steam velocity, humidity had been obtained.