In this paper, a numerical model of the coupling between astronomical tide and storm surge based on hydraulic model for estuary and coast (ECOM) is confirmed to be suitable for simulation of stormsurge in the Bohai Sea. The spatial distribution of extreme water level and storm current field caused by typhoons in October 2003 are simulated.It shows that extreme water level in deep water are smaller than shallow water and the spatial distribution of extreme water level is influenced by topography.Flow filed in Bohai Sea waters takes on an fluctuation in flow field, compensatory flow and other obvious features during storm surge, compared storm surge with astronomical tide, which is a significant difference in flow filed.