The characteristics and thermal evolution history of source rocks in the study area are clarified based on the pyrolysis analysis data of source rocks and PetroMod basin simulation technology. The hydrocarbon generation and expulsion modes are constructed by the hydrocarbon generation potential method to analyze the hydrocarbon generation and expulsion history and intensity. As a result，the influence of thermal evolution and hydrocarbon generation and expulsion of source rocks on oil and gas migration，accumulation，and distribution is revealed in the 3 ^rd Member of Eocene Shahejie Formation（Es₃）in Qikou Sag. The results show that the source rocks in the study area are generally in mature to highly mature evolution stages. The source rocks enter the hydrocarbon generation and expulsion threshold respectively when the vitrinite reflectance is about 0.53% and 0.83%. The hydrocarbon expulsion rate is 250 mg/g and the hydrocarbon expulsion efficiency is 65%. Hydrocarbon generation began briefly at the end of the late Eocene and stopped due to tectonic uplift in the early Oligocene. Hydrocarbon expulsion began in the middle Oligocene and reached the peak of hydrocarbon generation and expulsion at the end of the middle Oligocene. The consequent hydrocarbon generation and expulsion stopped again due to the tectonic movement at the end of the late Oligocene，and the whole hydrocarbon generation and expulsion process is basically consistent with the thermal evolution stage of source rocks. The hydrocarbon expulsion center is distributed along the periphery of Qibei Subsag to Qikou main sag，and the hydrocarbon expulsion intensity is up to 90×10⁶t/km² with strong hydrocarbon expulsion characteristics. The extensive hydrocarbon generation and expulsion distribution characteristics provide rich oil and gas sources and migration power for the adjacent uplift and slope of Qikou Sag. Additionally，the hydrocarbon has the characteristics of near source reservoir formation and long-distance lateral migration reservoir formation.