Abstract: Based on structural assemblages and direction in map view, structural patterns in seismic profiles and Bouguer gravity anomaly in the eastern Bohai Bay basin, we propose that the Bohai basin is characteristic of zonation of structural pattern. It can be divided into three zones from west to east. They are as follows:the western horseback belt, which developed many horsebacks and faults with small sags between horsebacks, and also had Bouguer gravity anomaly in irregular lump; the central sag belt, which was composed of the Bozhong and Liaozhong sags and horsebacks with few faults, and whose Bouguer gravity anomaly took on equi-axised clot and elliptic shape; the eastern horseback belt, which was composed of many interphase horsebacks and sags. Because the Tanlu fault cut through this belt, there developed many strike-slip faults and branch faults characteristic of string-shaped Bouguer gravity anomaly. The zonation of structural pattern is controlled by multi-phase tectonic movement related to development of the Tanlu fault, and this has an important effect on the distribution in the hydrocarbon in this area. The western and eastern horseback belts have become crucial target for hydrocarbon exploration due to their weaker movements and higher altitude.