A better understanding and modeling of breaking waves is important for coastal engineering. This article concerns the plunging wave break over a slope bottom considering unsteady, incompressible viscous flow with free surface. The method solves the two dimensional Naiver-Stokes equations for conservation of momentum, continuity equation, and full nonlinear kinematic free-surface equation for Newtonian fluids, as the governing equations in a vertical plane. A new mapping was developed to trace the deformed free surface encountered during wave propagation by transferring the governing equations from the physical domain to a computational domain. Finally a numerical scheme is developed using finite element modeling technique to predict the plunging wave break. The Arbitrary Lagrangian Eulerian (ALE) algorithm is employed in modeling wave propagation over sloping beaches. The results compared with other researches and show the good result.