隨者產品市場競爭日趨激烈，產品保證成為行銷產品的手法之一。賣方如何運用產品保證來推銷產品及維修策略來獲取最大利潤成為一個重要的主題。利潤的收入來源為賣方銷售產品及產品的延長保固與產品保固後的小修收費，故增加利潤與保固契約內容相關。若產品在保固期內失效時，則賣方為產品做小修。在保固期間內，當產品年齡到達一門檻值時，則賣方為產品實施不完美的預防保養以降低產品失效率；當產品在基礎和延長保固期間內發生失效時，賣方負責將產品維修至可運作狀態。若產品於延長保固後失效，則顧客需完全支付產品的維修費用。本論文以賣方的觀點，分析可維修產品在生命週期內各階段的支出與收入來建構產品總利潤數學模式並尋求最佳預防保養策略，最後以數值例子分析結果說明最佳預防保養策略及最大利潤。

As the rising competition from day to day, product warranty has become one of the marketing tactics. How to use both the product warranty to promote their products and maintenance strategies to maximize profits has become a serious issue for the sellers. The sellers will profit from products sales, product warranty, and product warranty extension, so it increases profits and warranty contracts relevant to the content.During the warranty period, if the product fails, the sellers will do minor repairs for the product. When the product age reaches a threshold value, the seller will implement an imperfect preventive maintenance for the product to reduce failure rate; when the product fails during the basic and extended warranty period, the seller is wholly responsible for product maintenance to be operational status. If the product fails after the extend warranty period, the customers were requested to pay fully for the product maintenance costs. In this paper, we take the viewpoint of the sellers to analyze the cost and income of repairable product in each product life cycle stages of to construct mathematical models for product gross margin and find the best strategies for preventive maintenance, the final results of the analysis shows a numerical example of the best preventive maintenance strategy and the maximum profits.

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