Currently Kongdian Formation is an important formation in the Dongying Sag, Jiyang Depression, Bohai Bay Basin, where oil and gas exploration has shifted to the deep layers. Restricted by the high degree of evolution, the hydrocarbon generation and expulsion potential of Ek2 source rocks in the eastern part of the southern slope of the Dongying sag is controversial. In order to explore the deep hydrocarbon-bearing system in the Dongying Sag and clarify the hydrocarbon generation and expulsion potential of the Ek2 source rocks , this paper discusses from the perspective of hydrocarbon-bearing detection combined with source rock analysis. Methods: Through the restoration of the paleogeomorphology during the depositional period of Ek2 Formation, combined with the seismic profile, we calrified the paleogeomorphology of the depositional period of Ek2 Formaion, and discuss the planar distribution characteristics of the Ek2 source rocks. Through geochemical analysis and thin section observation, the abundance, type and maturity of organic matter of Ek2 source rocks were studied, and the original organic carbon content of the highly mature Ek2source rocks was recovered, combined with fluid inclusion test, cold cathode luminescence, fluorescence observation on reservoir sampales of the Kongdian Formation in the east section of the south slope of Dongying Sag to identify the hydrocarbon generation and expulsion potential of the Ek2 source rocks. Results: It is believed that the Ek2 source rocks has a large distribution range, and the thicker source rock is developed in the subsidence center. The original organic carbon content of the Ek2 source rocks is relatively high, and the source of organic matter is mainly higher plants, belonging to type Ⅱ1-Ⅲ organic matter, with high maturity. The source rock has entered the gas generation stage, and is comprehensively assessed as medium-good source rocks. there are two stages of oil charging and one stage of gas charging: The first stage of oil charging occurred in the sedimentation period of the Es3 Formation; the second stage of oil charging occurred in the sedimentation period of the Dongying Formation; the third stage of gas charging occurred in the sedimentation period of the Plain Formation. Conclusions:The earliest hydrocarbon charging in Kongdian Formation occurred during the depositional period of Es3 Formation, Combined with the simulation results of hydrocarbon generation and expulsion of Paleogene source rocks in Dongying Sag, it is believed that the Ek2 source rocks gives the contribution of Kongdian Formation oil. The hydrocarbon generation and expulsion potential of Ek2 source rocks is identified by analyzing the development of Ek2 source rocks in combination with hydrocarbon generation and expulsion research, which is the basis for the research and identification of deep petroleum system in Dongying Sag.