Abstract: Mesozoic seafacies strata in the South China Sea Basin, 2 500~5 000 m thick and more than 125 000 km² in total area, were formed in the Ancient South China Sea. These sedimentary strata distribute mainly in eastern Zhujiangkou basin in the northern shelf of the South China Sea, and northwest Palawan, Liyue bank, and Nanweixi-Beikang basins and its vicinity in the southern South China Sea Basin. These two parts were partitioned by antique basement and Cenozoic oceanic crust. The suture belt of the Ancient South China Sea exists in an area from north Kalimantan to north Palawan. Biology fountain is mainly plankton that constitutes the source rock of seafacies in the South China Sea Basin, and kerogen type is III, which mainly generates gas. There exists a good matching relationship among hydrocarbon generation, fluid flow, and traps, and generates self-generation-and-self-reservation hydrocarbon reservoir, newgeneration-and-oldreservation reservoir and oldgeneration-and-newreservation reservoir. In summary, Mesozoic seafacies sedimentary rocks in the Ancient South China Sea Basin have a very good exploration potential.

Key words: seafacies strata, exploration potential, Mesozoic, the South China Sea Basin