Abstract: During leachate recirculation, a bioreactor landfill will experience more rapid and complete settlement, which is mostly attributed to the weight of municipal solid waste (MSW) and its biodegradation. The settlement of the landfill will cause the decrease of void ratio of the MSW, which will influence the permeability of the MSW and the leachate quantity that can be held in the bioreactor landfill. To study leachate recirculation in bioreactor landfills, based on the law of conservation of mass, the modified Darcy’s law and the Elagroudy’s settlement model, a new model is developed. Using this model, the transport law of injected leachate in bioreactor landfills is determined under unsaturated condition. The effects of various parameters (i.e. injection intensity, initial void ratio, water content and composition of MSW, etc.) on the water content of the MSW and unit surface area recirculation quantity are analyzed.