Yanji Basin was controlled by the extension faults with nearly SN strike and the combination of the east faults and west onlap was formed in the early period; at the late stage, the basin was dominated by the compressive folds with nearly EW strike and the structure with two south-north anticlines and a wide flat syncline was generated. Before the reform, the hydrocarbon source rock had been matured, but the hydrocarbon-generating threshold was rather differential. The end of Dalazi Formation and Longjing Formation are the main reservoir-accumulating stages, the late period of the later is the critical moment for the reservoir to enrich and accumulate. The central basin is characterized by well-developed, pretty complete and less-stripped formations and moreover the much better preser- ving conditions, so the light oil reservoirs are accumulated. Among them, the structural belts formed in the follow- ing subsags such as Dama, Qingchaguan, Dexin and so on. The stripped thicknesses are more than 700m in the northern and southern ends of the anticline, and furthermore the preserving conditions are very poor. The side close to the hydrocarbon source region can developed into a heavy oil reservoir with upper secondary gas reservoir.