In order to realize the overall optimum，the integrated optimization problem on Lot Sizing of the whole remanufacturing system with uncertain demand and reprocessing ratio is studied in this paper． First，a model describing the total disassembling and reprocessing cost is presented based on the defined Ｒatio of Lotsizing of reprocessing and disassembling and the variable reprocessing cost，which corresponds to their different quality conditions，of the disassembled parts． Second，an optimization model is proposed that considers all costs that occur during the remanufacturing process——including disassembling，reprocessing and reassembling sub-systems——and unknown procurement lead time，based on the principle of two-stage profit function to maximize the profit． Third，the optimal ratio of lot-sizing of disassembling and reprocessing，as well as lotsizing of disassembling，of reprocessing /purchasing，and of reassembling，are determined through the optimization model． Finally，the effects of different unit acquisition cost of remanufactured parts on lot-sizing of reprocessing，lot-sizing of purchasing，cost of disassembling and reprocessing，and total profit of the whole remanufacturing;the relationship between the ratio of reprocessing and disassembling and unit disassembling are discussed by numerical examples．