Abstract: The western exploratory area of Fengfuchuan Oilfield is a composite petroliferous region of multilayer and low permeability. The reservoir sedimentary is complicated. The sedimentary and evolution control the reservoir enrichment in a large part. This paper deeply analyzed the sedimentary facies, provenance and the sedimentary structure of Chang 2, Chang 4+5 and Chang 6 in the main oil-bearing series of Yanchang formation, then multiphase system of sedimentary succession was established and sedimentary evolution was analyzed. The results indicated that Yanchang formation mainly developed delta sedimentary system; sediments were imported into Basin from northeast to southwest through distributary channel and channel distribution in different period of the development had a good inheritance which fully illustrated the deposit scale and characteristics of sedimentary evolution of Yanchang formation in the main oil-bearing segment; better inheritance of the channel distribution and a good reservoir cap assemblage in the same layer will provide reliable support for the next exploration of favorable reservoir enrichment zone.