A viscous two-phase numerical model based on the Immersed Boundary Method (IBM) and Volume of Fluid (VOF) method has been employed. In this model, the direct-forcing IBM and VOF method are applied to present the rigid boundary and capture the free surface respectively. Due to change of density and viscosity on the free surface, the density and viscosity are regarded as variables in the governing equations. The feasibility and accuracy of model are validated by simulating the dam-break with an obstacle. The simulation results agree well with other researcher's simulation results and experimental observation.