Abstract: In order to reveal the oil and gas exploration prospect in the Xisha Trough Basin, this paper is donated to the oil and gas system of the basin. Research results suggest that Cenozoic oil and gas systems are well developed in the Xisha Trough Basin. Source rocks include the Eocene laustrine mudstone and Oligocene marine mudstone. Reservoirs consist of the Eocene lake deposits, deltaic deposits and channel filling sandstones, Oligocene offshore and shallow marine deposits, marine delta deposits and deep water fan sandstones. The cap rock include three layers: Eocene lacustrine mudstone, Oligocene marine mudstone and Miocene-Quaternary bathyal-abysmal mudstone. The oil and gas system was mainly formed in Miocene in the Xisha Trough Basin, where all the geological events matched very well. The Cenozoic oil and gas system can be further subdivided into four migration and accumulation units. The central depression and the northern fault ladder belt adjacent to the central depression and the west parts of the south depression are the principal exploration targets recommended.