For the development of offshore horizontal wells, the study of remaining oil should be based on clear main control factors. Research on residual oil distribution under main control factors by numerical simulation method,the research showed that for the oilfields which developed by horizontal wells predominantly, the main controlling factor of remaining oil should be clear as the basis of numerical simulation. in this paper, both the position and digging direction of the enrichment of remaining oil were summarized, it also gives the conclusion that physical conditions, sedimentary microfacies, interlayer, development method were the most important influence factors on remaining oil which characterize the oilfield. Among them, the remaining oil in the interlayer interlayer and multi⁃stage river channel superposition control is the heaviest, which is the main target for future adjustment and potential tapping.