The bottom water reservoir of fluvial facies in Caofeidian oilfields is a kind of important reservoir type in the Bohai sea，developed by irregular horizontal well pattern. Most of the oil reservoirs have entered into middle-high water cut stage with low recovery efficiency. It is urgent to research distribution law and main control factors of the remaining oil for guiding next overall adjustment. The lower member of GuanⅢ（NgⅢ）oil formation in Caofeidian oilfields is a main development unit with massive OIP，many production wells，small gas cap and low amplitude structure at high water cut stage.By analysis of geological data and production data，five factors controlling the distribution of remaining oil in the study area were concluded as structure factor（micromorphology of structure，faults with small fault throw and so on），interlayer of fluvial flood-plain，difference of oil-water contact，early development policy and current production well pattern. Remaining oil distribution has some regularity in the upper and the lower development units separated by the second-period interlayer.Remaining oil in the upper unit mainly distributes in the area with imperfect well pattern of oil ring. Remaining oil in the lower unit distributes mainly in areas with lower oil-water contact and imperfect well pattern of western oil reservoir，in the central region between lateral section and gas-oil contact，in the structural high part under the fourth-period interlayer and in areas near faults far away from production well.