Abstract: Abstract：Based on seismic information and applying multi-cyclic tension-followed-by-compression tectonic evolution theory for China’s oil and gas-bearing basins, this paper systematically expounds the evolutionary process and formation mechanism of Eogene—Neogene geological structure in the sea area of Bohai Gulf basin. With high-quality exploration seismic information, the petroleum tectonic styles in the sea area of Bohai Gulf basin are divided into three types (penetration, separation and infiltration) and thirteen subtypes. The complex tectonic types and compound oil and gas reservoirs (fields) are described in the end of this paper.