Abstract: Through detailed study of physical prosperities and geochemical characteristics of heavy oil in Chunfeng oilfield of Chepaizi area,heavy oil mainly comes from source rock of Permian,companying with some water bath and oxidation. After integrated analysis of the reservoir fluid inclusion characteristics,the generation and expulsion history of the source rock and the diagenesis of the reservoir rock and structure movement,heavy oil has been found to be the product of ancient reservoir adjustment.The accumulation mode is far source and stepped migration mode.The oil from Permian first accumulated in the Cheguai faulted belt,the structure movement result in the destroy and reconstruct of the reservoir,the hydrocarbon migrated to the Chunfeng oilfield.Later,under biodegradation,heavy oil reservoirs were formed.