Abstract: Based on analysis of hydrocarbon expulsion mechanism in different stages, the way of stress effect on hydrocarbon expulsion is discussed, and theoretical model of hydrocarbon expulsion with stress effect is developed. By these models, the stress effect on hydrocarbon expulsion is defined on two aspects: pathway formation of hydrocarbon expulsion (microfracture) and as a power of primary oil migration (causing the change of fluid pressure of source rock). The result shows that the stress component which has main effect on hydrocarbon expulsion is maximum differential stress, and the direction of hydrocarbon expulsion is parallel to microfracture, which is parallel to maximum main stress. It is also shown that, in different kind of basins, the way and result of stress effect on hydrocarbon expulsion is different, in which compressive basin has relative bigger effect, and extensional basin has smaller one, and it is the most propitious to hydrocarbon expulsion in active tectonic stage.