K/N cold- standby redundant system is an important way of improving the system reliability.However,inthe existing analytical models of this system,the scrap of repairable spare parts are not taken into consideration.Tosolve this problem,in this paper,first,the characteristics and working procedure of K/N cold- standby redundantsystem are analyzed.Next,by taking the minimum maintenance cost as the optimization target,a single- indenturetwo- echelon optimization model of repairable spare parts is proposed.Then,based on the allocation and modelingtheory of repairable spare parts,the analysis process and method considering the spare parts- supporting efficiencywith scraps are investigated. Moreover, the optimization model is solved via the marginal analysis,and the demandsfor spare parts are subsequently forecasted. Finally,some examples are presented to verify the feasibility and appli-cability of the proposed method.