The development of offshore oilfield has time limited efficacy. Based on controlling the production decline rate, keeping high rate of oil production is the basic requirement for the development benefit of offshore oilfield. Based on the characteristics and development requirements of offshore oilfield development, it was established a method and steps for determining the reasonable rate of oil production in the later stage of waterflooding development of offshore oilfield. Firstly, to determine the maximum and feasible rate range of production, it was established the evaluation method for the production capacity at different development stage. Secondly, under different rates of fluid production, it was made the re- lation chart among the production decline rate, the water cut, and the recovery degree of recoverable reserves, to deter- mine the oil production rate which can meet the limit of decline rate. Thirdly, according to the economic benefit limit of oilfield development, the lowest rate of oil production was determined. Finally, overall considering the conditions of oil- field productivity, requirements of stable production and decline control, and economic and technical limits, it was determined the reasonable rate range of oil production in the later stage of offshore oilfield development. The method was applied in PLA -30ilfield. The application results indicated that the method is simple and feasible, and the calculation resuits are closer to the actual.