Abstract: In order to determine the main stages of the hydrocarbon accumulation of the Paleozoic reservoir in Rub Al Khali Basin, four key methods are applied in this paper including hydrocarbon generation and expulsion history simulation, measurements of fluid inclusions homogenization temperature and Illite K-Ar dating.The simulation of hydrocarbon generation and expulsion history of Well S2 shows that hydrocarbon generation and expulsion of the Silurian source rocks in the central depression peaked in the Triassic and Cretaceous.The simulation of hydrocarbon generation and expulsion history of Well A2 shows that the hydrocarbon generation and expulsion of the Silurian source rocks in the slope zone peaked in the Early Cretaceous.The analysis of homogenization temperature of fluid inclusions of Well S2 shows that most of the samples can be divided into two main stages and only some samples can be divided into three stages.In combination with the geothermal history, these three stages are the Triassic, Early Cretaceous and Late Cretaceous respectively.In contrast, the homogenization temperature of fluid inclusions of Well S2 in the slope zone can be separated into two stages, indicating that at least two periods of oil and gas charging occurred in the Ordovician.In combination with the geothermal history, the two periods are in the Early Cretaceous and Late Cretaceous respectively.The result of Illite K-Ar dating shows that the hydrocarbon accumulation in the Paleozoic of Well S2 in the central depression occurred mainly in the Triassic and Late Jurassic-Early Cretaceous.A comprehensive analysis indicates that the hydrocarbon accumulation of the Paleozoic reservoir in Rub Al Khali Basin mainly occurred in three periods.The first one is the Triassic, the second one is the Early Cretaceous and the last one is the Late Cretaceous.The hydrocarbon accumulations formed in the first stage are mainly distributed in the central depression, and that in the third stage are mainly distributed in the slope zone, and that in the second stage occurred in both the central depression and slope zone.

Key words: authigenic illite, hydrocarbon generation and expulsion, accumulation stage, fluid inclusion, Rub Al Khali Basin