Abstract: For the purpose of potential development in the old areas and increasing oil recovery of the late development period, through detailed description and explanation of fault system in Ying 8 block area in Dongxin oilfield,with the combination of geology research and dynamic information,classification standard of regional faults is established.It is considered that faults are less developed in the west of study area, developed in the east fault,and more developed in lower sand layers than upper sand layers.Detailed structure interpretation and micro- structure study helps in solving conflicts between production wells and water injection wells.This may provide guidance and basis for confirmation of remaining oil distribution and deployment of development adjustment programs.