This paper was concerned with a vertical two-dimensional (2D) flow model with free surface. The water governing equations were discretized with finite difference method. The function of volume method was employed to track the moving free surface. The model was used to predict the characteristics of dam-break flow in a 2D vertical plane. The surface profile and time averaged velocity were calculated, which shows the proposed model can be capable of capturing sharp water and gas interface configuration as time elapses.