The sea level reached its maximum off East China at 7 000 a B.P., and the Yellow River delta was not formed then. The western part of the ancient Bohai Sea was very wide at that time. Based on the previous studies of seismic profiles and coring data, paleocoastlines and paleotopography were roughly recovered in this paper. A three dimensional numerical model based on the hydrodynamic sediment model of ECOMSED was established to simulate the tidal process in the Bohai Sea during the transgression maximum and the present. The results show that the tidal currents of the ancient Bohai Sea during the period of the maximum transgression (7 ka B.P.) were much weaker than those in the present time, especially in the west part of the ancient Bohai Sea, as a result of greater water depth, wider coast zone and weaker tidal waves from the Yellow Sea.
