Abstract: Research status and existing problems of wave numerical models for shallow water at the coastal and estuarine zone are generalized,the developing history of forecasting waves with energy balance equation is also discussed.The third generation wave model Simulating waves Nearshore(SWAN),based on the most advanced wave study achievements,is described in great detil here.In additiion,the applicability,numerical characteristic,functionality and limitation of the model are interpreted. The action balance equation,its discrete demand,the method dealing boundary condition,and source terms(the wind input,the energy dissipation and nonlinear wave-wave interactions) are detailed discussed,and special emphasis is put on the triad wave-wave interactions. The SWAN model is applied to simulate the significant wave height and average period at the Haian bay,and the influence of nonlinear wave-wave interaction term on the simulation results is analyzed. Finally,the application foreground and study tendency of the model is discussed,too.