研究由两个内可逆卡诺制冷循环构成的无中间热源的联合制冷循环有限时间热力学最优性能。基于一类较为普遍的物理模型，导出其制冷量与制冷系数间的基本关系，再根据活塞式模型循环和定常流模型循环的基本特征，得到两种模型联合到冷循环的最佳制冷率密度与制冷系数间的关系。对前者，与前人所得结果相同；对后者，获得了一些新的有意义的结论。有关结果还可推广到由两个以上制冷循环构成的联合制令循环。 The optimal performance of finite-time thermodynamics for a combined refrigeration cycle with two intermediate reversible Carnot refrigeration cycles without intermediate heat source was investigated. Based on a more general physical model, the basic relationship between cooling capacity and refrigeration coefficient was deduced. Based on the basic characteristics of piston model cycle and steady flow model cycle, the optimal cooling rate And the relationship between refrigeration coefficient. For the former, the result is the same as that of the predecessors; for the latter, some new and significant conclusions are obtained. The results can also be extended to a combined cycle of more than two refrigeration cycles.