Abstract: The study of hydrodynamics in the surf and swash zone is essential to understanding the nearshore sediment transport and coast beach evolution.A numerical model is developed to analyze the flow mechanism in surf and swash zone under the influence of submerged breakwater.The twodimensional Reynolds Averaged NavierStokes equations,together with a nonlinear κ-ε turbulence model,and a finite difference method are employed in the model development.For a better simulation of wave breaking,a piecewise linear interface construction volume of fluid technique is utilized,which has good accuracy in describing air/water surfaces.The numerical model is validated with the experimental data and used to analyze the influence of submerged breakwater.The numerical results indicate that the location of breaking point and hydrodynamic characteristics in surf and swash zone are changed by the submerged breakwater.The wave height (H),wave length (L),depth of submergence (R) and crest width (B) play an important role in influencing hydrodynamic processes in these two zones.Under the same incident wave,the maximum turbulent kinetic energy and turbulence dissipation rates in two zones decrease as B/R increases.The dimensionless numbers of Re,Fr and St are deduced form RANS equations and used to describe hydrodynamics in surf and swash zones.The wave breaking could take place near the shore as RL/BH increases,meanwhile Re and Fr increases,and at the same time St decreases.