Abstract: Pyrolysis of two kerogens isolated from Niu?15 well (E3s3) and Wang?120 well (E2 s14 ) source rocks in the Dongying sag of Bohai Bay basin was performed in a confined system under pressure of 50 MPa at temperature of 2°C/h and 20°C/h. The generated products were extracted with solvent and separated using micro?column chromatography into group?type fractions like saturates, aromatics, resin and as phaltene. Kinetics 2000 software was employed to fit the kinetic parameters, including the total hydrocarbons and group composition produced from the two kerogen samples. The generation kinetics study of crude oil and its group?type fractions from the kerogens shows that the oil thresholds that the E3s3 and the E2 s14 source rocks were generated at about 4.26 ×106 a and 24.85×106 a, respectively, and the E3s3 source rocks are still in the main phase of hydrocarbon generation, while the E2 s14 source rocks in the late phase. At present, the yields of saturates, aromatics, resin and asphaltene from the E3s3 source rocks are 222.03 mg/g, 71.30 mg/g, 62.37 mg/g and 50.04 mg/g, while those from the E2 s14 source rocks are 280.94 mg/g, 95.98 mg/g, 66.79 mg/g and 53.82 mg/g, respectively