Abstract: Petroleum geological conditions are obviously different between the northern and southern continental marginal basins of the South China Sea. At present, the oil and gas production of the southern basins are much higher than that from the northern basins. According to their depositional characters, the reservoir/cap assemblages in the northern and southern continental marginal basins of South China Sea can be grouped into four types:continental sandstone + local cap, paralic sandstone +local or regional cap, neritic clastic sandstone/carbonate/biological reef + regional cap of neritic shale and clastic rock of deep water/neritic sandstone + cap of shale of deep water. Compared to the north basins, the south basins are extensively dominated by the reservoir-cap assemblage of carbonate + marine facies shale. Results of this study suggest that tectonic activity is the first controlling factor of the differences of reservoir-cap assemblages between the northern and the southern continental marginal basins. Evolution of regional geology and environmental settings are also important.