A universal irreversible refrigeration cycle model which includes the irreversibility of heat transfer across finite temperature differences, the heat leak loss between the external heat reservoirs and the internal irreversibility of the working fluid is used to analyze the performance of a multi-stage combined refrigeration system. The ecological function is taken as an objective function for optimization. The maximum ecological function, its corresponding coefficient of performance, rate of refrigeration and rate of entropy production are determined. The optimal problems relative to the ecological function are discussed. Some characteristic curves of the refrigeration system are presented. The results obtained here are suitable for an arbitrary stage irreversible combined refrigeration system.