Objectives：The quantitative study methods and its application of the depth of oil and gas vertically downward migration along faults is the key to oil and gas exploration in the upper generation and lower accumulation pattern of petroliferous basin. To study the quantitative study methods of the maximum depth of oil and gas vertically downward migration along faults. Methods:Based on the relationship between paleo- overpressure of source rocks and the depth of vertically downward oil and gas migration along faults, the paleo- overpressure minimum source rock needed for vertical downward and migration along faults of oil and gas was determined(or the resistance of oil and gas migration along fault zones). Based on the dynamic conditions required for oil—gas vertical inversion and migration along faults, we found a series of research methods of the maximum depth of oil and gas vertically downward migration and apply it to a source rock formation vertically downward migration along faults. Ressults: It turned out that the maximum depth of vertically downward migration along faults of a source rock formation in Sanzhao depression of Songliao basin can reach 400m, which mainly distributed in four local areas：Shu119 well in the eastern margin , Zhao 13 well in the western margin, Songshen 1 well in the northern margin and the center of sag. Conclusions: The maximum depth of the vertical downward migration along faults of the oil from the four high- value areas to the surrounding rocks of Qing1 Member to the periphery gradually decreased and is reduced below 100m in the northern and the edge of depression, which is basically match with the depth distribution of current found bottom oil layer in Fuyang reservoir of Sanzhao depression. This indicates that it is feasible to use the method to quantitatively study the maximum depth of oil and gas vertically downward migration along faults.