Abstract: The deep layers of Songliao Basin include Jurassic Huoshiling Formation, Lower Cretaceous Shahezi Formation and fault-depression stratum of Yingcheng Formation, and Lower Cretaceous depression strata of Denglouku Formation and Mem.I+II of Quantou Formation. The fault controlling the depression is in the NNE and NW directions. The fault depression is distributed along Nenjiang fracture belt, Sunwu-Shuangliao fracture belt and Harbin-Siping fracture belt. The sedimentary time for Huoshiling-Shahezi Formation is the time for the fault depression to be extended at a large scale. At the end of sedimentation for Shahezi Formation, the large-scale reversal takes place, laying the foundation for reformation of strata in the fault depression period. Mudstone of lake facies and coal measure are the most important hydrocarbon source stratum series during the faulted depression period. The three sets of regional cap rock-Mem. II of Denglouku Formation, Mem.I and II of Quantou Formation and Mem.I of Qing shankou Formationseparate four sets of natural gas source-reservoir-caprock assemblages. Close to the palaeohigh of the source depression, the fracture belt controlling the depression and the palaeostructure in the fault depression are the favorable zone for natural gas accumulation