Abstract: In order to reveal the relationship between the development and evolution of complicated fracture system and the formation of reservoir in south fault zone of Gaoyou Sag, Xuzhuang-Zhudun Area, through calculation of the erosion of the unconformable stratum and analysis of the structural evolution profile, the evolutional history of fault in Xuzhuang-Zhudun Area has been summarized systematically.Fault activity was the most intensive during Wubao Movement and Sanduo Movement stage, and the stratum of Xuzhuang-Zhudun suffered from erosion strongly.The development order of the main faults is as follows following:Fault Zhen ①, Fault Ji ③, Fault Zhen ②' and Fault Zhen ②.In different geological period and different planar location, the intensity of fault development is quite different for the same faults.On one hand, the fault activity caused the development of a series of fault blocks;on the other hand, the faults also the main pathways for vertical petroleum migration.Therefore, a series of fault block reservoir formed in this region.