Abstract: A large number of reefs developed in the Dongsha sea area of the northern South China Sea during the early Miocene, which are rich in oil and natural gas resources. Based on the high resolution seismic data in this area, this paper mainly analyzes the types and spatial distribution characteristics of reefs in the region. Combined with the research results of regional source rocks in recent years, the hydrocarbon accumulation model of reefs in Dongsha sea area has been perfected.The results show that there are four types of reefs in Dongsha sea area:platform marginal reefs, massive reefs, layered reefs, and tower reefs. These reefs are mainly distributed in the southwest and south of Dongsha Uplift.The results of oil and gas drilling show that the Eocene and Oligocene of Baiyun Sag in the southern part of the Dongsha Uplift also have good hydrocarbon generation capacity. Based on the spatial distribution relationship between source rocks, reefs and drainage systems, it is pointed out that the reefs in Dongsha sea area have the bidirectional oil and gas accumulation in Huizhou Sag and Baiyun Sag. The reefs in the northern part of Baiyun Sag also have good potential for oil and gas. They are important directions of oil and gas exploration in the future.