“瞬息萬變”，可以用來形容現今的全球化市場，企業在供應鏈上的管理課題能否做好更加關鍵，比如：零售商要求改善服務水準和減低總生產成本以及來自客戶需求不確定性，而採購策略在供應鏈管理上扮演相當重要的角色。採購策略經常使用寄售(Consignment stock)與競標(Competitive bidding)兩種方法來做存貨的控管。另外一方面，為達到降低存貨之目的，需求的變異性和不確定性會影響公司降低商總需求的變異。從研究中發現，當競標產品轉換至寄售產品和寄售產品轉換至競標產品時，如何做產品轉換以及轉換多少比例能讓總成本降到最低，並得到管理的實務意義。然而，公司在選擇採購策略的同時，不僅要思考採購單價的高低，還須考慮其他因素對成本的影響。當公司面對競標或寄售的採購策略選擇時，此成本模式可作為決策者對於總成本衡量的參考工具，搭配上成本考量，微調轉換率和策略轉換，進一步定義出公司合適的最佳狀況。 Rapidly changing can be used to describe market of globalization in the modern time. It is more critical that whether the issue of supply chain can be well managed in enterprises. For example: the pressure from customers’ demand uncertainty, and the distributor’s request to improve the service level and reduce the cost, and procurement strategy play a very important role in the supply chain management. Consignment stock and competitive bidding often be used to control stock. On the other hand, in order to achieve the purpose of reducing inventories, demand variability and uncertainty will affect the company to reduce the variation of total demand. When two products used two strategies to substitute, how much to switch, and when do the switching can be reduced the total cost, and we can get some management implications. On the other hand, it not only think the procurement price, but also need to consider factors when companies choice procurement strategies. So if companies face to choice consignment stock or competitive bidding decision, this cost model could as decision-makers’ tool for the measurable of total cost, and with cost consideration, switching rate, or strategy transfer, define the optimization for companies.