Abstract: Influenced by the specific geopolitical position and the complicated engineering geological background, oil exploration in the deepwater basins of the SCS is much delayed. It has led to a lack of understanding of hydrocarbon accumulation conditions, favorable enrichment areas and main controlling factors. Through system analysis and case studies of some typical fields, based on the regional geological background, and the patterns of "source rocks, migration, accumulation and preservation", this paper reveals four petroleum plays, including the Pre-Tertiary basement play, lower play, middle play and upper play. At the same time, the hydrocarbon favorable accumulation zones and the main controlling factors of each play are described and discussed. From the study, the following conclusions are reached. First, the middle and lower plays are the main ones for the northern part of SCS. Second, the middle and upper plays are the main ones for the southern part of SCS. Third, the upper play is the most important one for deepwater areas.