Abstract: The petroleum in the Subei basin is famous for poor,small,beraking to pieces,and scattering in the exploration history of Chinese petroleum,and it is a typical case of the most complex and small fault-lock in the East of China.But the fault-block of Tianchang halfgraben-like depression is more breaking and scattering.Formation of complex fault system depends on its special tectogenesis background,and oil-gas migration and oil reservoir formation are closely impartibility with it.Analysis of fault system is a basis for futher realizing oil exploration and development.Fault system research mast not only master part,but also master all.This paper emphasizes method study of fault system,which is also to provide a reference for petroleum exploration in similar tectonic background.