Abstract: The Sha?3 member (Es3) in western Gubei sub?sag in Bohai Bay basin mainly develops fan delta, slump turbidite fan, inshore underwater fan and lacustrine sedimentary systems. The development of fan delta and inshore underwater fan are of successive and stage nature, and these fans develop in weakening trend. The hydrocarbon accumulation in this area is mainly controlled by sedimentary system. The mature source rocks were formed in the lacustrine environment, and reservoirs with good source?reservoir?cap rock assemblage are commonly found in each type of sedimentary system. The lithologic trap controlled by sedimentary system is main type of traps, followed by fault?screened trap. Also, it is recognized that the short distance of petroleum migration, good transport condition of matrix sand body and single petroleum migration and accumulation modes should make the lithologic reservoir become the main target for petroleum exploration in this area