Abstract: Typical extensional structural patterns, cut into a series of complex fault noses and fault blocks by faults of different levels, form under regional extension force in Biyang depression. Based on study of structural features of the complex fault noses and fault blocks in different areas, fault block group patterns are classified into graben and step types and their control on oil accumulation are analyzed. Inherited nose- like structures control not only the direction of hydrocarbon migration, but also the level of hydrocarbon enrichment. Faults are the main factor that control hydrocarbon accumulations and can act both as migration pathways and barriers of hydrocarbon. Therefore, the complex fault block groups in Biyang depression have the geological conditions to form large hydrocarbon enrichment areas.