現今的供應鏈管理當中，許多零售商向同一製造商批發相同的產品來販賣，由於零售商各自的實力和競爭力不同，使得他們相對於競爭者具有一定程度的替代性。零售商在訂價時必須先考量競爭者的價格，才能使本身利潤達到最大；同樣地，競爭者也是根據對手的情況來訂價。當市場的顧客需求改變時，零售商之間為了維護自己的利益將開始進行價格競爭，藉此決定本身新的賣價和訂購量。
本論文即在建立一個數學模型來討論雙占市場中的最佳訂價和最適訂購量，利用線性需求函數來分析需求環境變動前後零售商之間的競爭局勢。第一家廠商先感受到需求變動而改變訂價，第二家廠商隨後採取因應措施，第一家廠商在第二家廠商行動之後也做出新的動作，彼此反覆追逐訂價的過程最後將達到均勢狀況。此數學模型的每項市場參數都會影響廠商的決策形成，本文將分析個別參數增加或減少時對零售商之賣價和訂購量產生的效應，也針對參數的交互作用對兩零售商之間的競爭活動進行探討。

In modern supply chain management, most of retailers sell the same products which get from one supplier. The power of every retailer is different, so one’s degree of substitutability differs form each other. If the manager wants to make his profit maximize, he must consider the competitor’s price first. On the contrary, the competitor also is. When the customers demand of market changes, they have to decide new selling price and ordering quantity. Similarly, both sides begin to price competition to protect each profit.
Hence, this paper provides a model to discuss the optimal pricing and ordering quantity under a duopoly market. This paper adopts a general of linear demand function to analyze two retailers’ prices and quantities before and after the demand environment shock. We would like provide an example to illustrate some observations. Furthermore, we present how the parameters affect the decision making on prices and quantities. We discuss the interaction of the parameters make what kinds of influence on two retailers at the end.

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