Abstract: The steam-water separator and the containment spray system are key equipment of nuclear power plant. There are many physical phenomena, such as discrete droplet motion in flow field, droplet collision and droplet phase change etc., during the operation process of the steam-water separator and the containment spray system. Based on the Euler-Lagrange method, the discrete droplet motion model was established, which includes independent models, such as the single and many droplets motion model, the droplet collision model, the two-way-coupling between droplet and continuous flow model, the droplet phase change model, the film droplet produced by bubble bursting at a free water surface model, the droplet extinction model etc., and their boundary conditions, to describe droplet behavior at flow field. Some examples about application of the discrete droplet motion model were shown to describe the discrete droplet motion behavior in the physical phenomena of evaporation, condensation and spray. Finally, some topics about the discrete droplet motion model and its computational method were shown to hope more researchers who have interests to push forward its development.