Abstract: Based on the seismic and well data up to present and their correlation with adjacent areas,the author discussed in this paper the geological background of the Mesozoic in the Nansha area of the South China Sea,with emphasis on tectonic evolution,stratigraphic correlation and seismic data interpretation. Comparison was made for the first hand well data from this region with the data from adjacent areas onland and offshore.It is recognized that the gas-prone Cretaceous is a key source rock with high total organic carbon(TOC)and ⅢI₂-Ⅲ type of kerogen,and favorable to the formation of various hydrocarbon plays. It is suggested that the pre-Tertiary deposits be significant targets for hydrocarbon exploration in both the South China Sea and the intercontinental basins in South China.