In order to address the core challenge of insufficient hydrocarbon supply from the traditional main source rock (the second member of the Liushagang Formation, E?l?) during deep exploration in the Wushi Sag of the Beibuwan Basin, and to correct the long-standing misconception that the third member of the Liushagang Formation (E?l?) serves only as a reservoir rock, this study aims to clarify the exploration value of E?l? as an effective independent source rock. Organic-inorganic integrated geochemical analyses, including rock pyrolysis, gas chromatography-mass spectrometry (GC-MS) and trace element analysis, were carried out to characterize the source rock quality, biomarker features and depositional environment. Semi-closed system thermal simulation experiments and hydrocarbon generation kinetic modeling were performed to quantitatively reveal the hydrocarbon generation and evolution processes and mechanisms. The results show that the E?l? source rocks have total organic carbon (TOC) contents ranging from 0.4% to 11.5% with an average of 2.2%, and an average hydrocarbon generation potential (S?+S?) of 10.4 mg/g. They are dominated by type Ⅱ? kerogen, with an average vitrinite reflectance (Ro) of 0.72%, and are mainly in the peak oil generation stage. The source rocks formed in a freshwater weak oxidation-weak reduction environment under an arid and hot paleoclimate, with moderate paleoproductivity and mixed organic matter input dominated by terrestrial higher plants and supplemented by lower aquatic organisms. The total oil yield reaches a peak of 172.58 mg/gTOC at EasyRo values of 1.29% to 1.41%, and the oil generation window is significantly wider than the traditional model. The gaseous hydrocarbon yield increases continuously with thermal maturity. Extensive cracking of residual oil occurs when EasyRo exceeds 1.29%, which provides an important material basis for late natural gas accumulation. Kinetic parameters show that the main activation energy for oil generation is 220 kJ/mol, and that for gas generation is 260 kJ/mol. The mixed parent material causes a broad distribution of oil generation activation energy, which essentially determines the characteristics of co-generation of oil and gas and multi-stage continuous hydrocarbon supply of the E?l? source rocks. This study confirms that the E?l? is an important independent source rock. It significantly extends the deep hydrocarbon exploration scope in the Wushi Sag and provides a critical scientific basis for deep exploration deployment in this region.