Abstract: Based on the analysis of the regional structure,this paper mainly focus on the discuss of the distribution,characteristics,and process of the formation of the sub-fault around major fault and its controlling to the accumulation of oil and gas in complex fault-block oil-field,Taking the Xianhezhuang Oil-Field in the central syncline belts in Dongying depression as an example.The result suggests that the sub faults in the conjugated-area of explored blocks and its edges,which control the new-prospected oil bearing block, plays an important role in the reservoir increment of the old oil-explored field.