The Bohai Sea area, offshore of the Bohai Bay Basin, is one of the most petroliferous regions in China, with proven original oil in place of approximately 2.4 × 10⁹ m³ (150.94 × 10⁸ bbl) and proven original gas in place of over 5 × 10¹² m³ (1.76 × 10¹³ ft³). Cumulative oil production is over 50 million tons (3.5 × 10⁸ bbl). In this study, using the limited data on source rock thickness, core samples, and Rock-Eval pyrolysis along with sedimentary facies analysis, source rock characteristics of different depositional settings were identified, and the thickness, richness, organic matter type, and thermal evolution of four sets of source rocks in the Bohai Sea area— the second member of Dongying Formation (E₃d₂), the third member of Dongying Formation (E₃d₃), the first and second members of Shahejie Formation (E₂s_1-2), and the third member of Shahejie Formation (E₂s₃)—were predicted and evaluated. Subsequently, the intensity and history of hydrocarbon expulsion for different sags was systematically compared and analyzed. The greatest thickness of the four sets of source rocks in the Bohai Sea area is 400–800 m (1300–2600 ft). The average richness of the organic matter of these source rocks is 1.74%–2.87%. The E₂s₃ set has the highest organic matter abundance; E₂s_1-2 has the lowest. The organic matter of these source rocks is mainly type I and type II, but their evolutions differ. The vitrinite reflectance of E₃d₂ is 0.5%–1.0%, that of E₃d₃ is 0.7%–1.25%, that of E₂s_1-2 is 0.75%–1.75%, and that of E₂s₃ is 0.75%–2.0%. The cumulative hydrocarbon expulsion of the four sets of rocks is 4.14 × 10¹⁰ t (2.90 × 10¹¹ bbl). The E₂s_1-2 set has the greatest expulsion amount: 1.75 × 10¹⁰ t (1.22 × 10¹¹ bbl). The peak stages of hydrocarbon expulsion of the four sets of source rocks were during Neogene Minghuazhen Formation (12.2–2.0 Ma) and Neogene Guantao Formation (16.6–12.0 Ma). The Bozhong sag expelled the most hydrocarbons, followed by the Liaozhong, Qikou, and Huanghekou sags.