Dongpu sag is a typical hydrocarbon rich sag in Bohai Bay Basin. Based on the methods of generation and expulsion stages of major hydrocarbon source rocks and fluid inclusion analysis, the oil and gas accumulation periods of Paleogene in Dongpu sag were studied. The results showed that the hydrocarbon accumulation period was divided into two stages. The first stage was from late Dongying deposition period to the early uplift stages, and the second was from the late Minghuazhen deposition period to the Quaternary. The first stage was the main accumulation stage. The accumulation periods of different parts and different layers was studied and compared. The main controlling factors of the differences were analyzed. The oil and gas reservoirs generated in the first phase were extensively distributed and covering all the area; By contrast the oil and gas reservoirs generated in the second stage were mainly distributed in the area near the hydrocarbon generation sags. Reservoirs formed in the fist period were extensively distributed and covering all the area. By contrast, reservoirs generated in the second period were mainly distributed near the hydrocarbon generation sags. Reservoirs formed in the second period were mainly concentrated in the sourse rock layers. The differences were mainly controlled by fault activity and the distribution of high mature source rocks.