Abstract: A new-type practical hydrocarbon-expulsion model is suggested in this paper. According to this model, hydrocarbon expulsion can be divided into monofactor and bifactor two stages. During the monofactor hydrocarbon-expulsion stage, oil saturation is the only controling factor to the expulsion of hydrocarbons, and the driving force of hydrocarbon expulsion is compaction; in the difactor hydrocarbon-expulsion stage, the expulsion of hydrocarbons is doubly controlled by critical oil saturation and critical fracturing pressure, and the driving force of hydrocarbon expulsion is fluid overpressure. This breaks through the limitations to monostage or monofactor hydrocarbon-expulsion simulation before, refrains from studying on complex facies during hydrocarbon expulsion, and avoids the accumulation of errors. The key of the model is dividing standards of the two stages, the determination of critical oil saturation (S_c) and critical fracturing pressure (p_c), and the acquirement of fluid overpressure. This model has obtained good application effects during the quantitative evaluation on the hydrocabon source rocks of the Jiazhangsi Sag in the eastern depression of the Liaohe Basin.