Abstract: The simulated area which is 75 kilometers long and 50 kilometers wide of Hongkong-Zhuhai-Macao Bridge tidal physical model is larger than 2,100 km2 in Lingdingyang estuary.How to deal with a cluster of piles with bridge piers is the most important problem.If we just consider it as a small scale model to use the geometry simulation for a single pile,the model won′t have similar resistance.So based on the principle of tidal movement similarity,the total resistance similarity of the piles with bridge piers is considered to generalize the model.After the physic model′s flow simulation,the reserch results show that the model is reasonable in generalizing the cluster of piles with bridge piers and the boundary condition.The model is well used for simulating the impacts upon flow movement caused by the bridge construction,and it provides an available method for the physical model design of huge cross-sea bridges.