存貨是企業經營中不可或缺的一環，在現今市場變化大與競爭激烈的情況下，建立良好的存貨控制對企業而言是重要的課題，因此企業對於存貨的控制必須做謹慎的規劃。本研究主要目的為探討額外費用投資降低不良率之品質提升和更新理論觀念導入非完美品質生產存貨系統過程來推導出每單位時間期望總利潤，尋求投資品質改善成本之最佳存貨策略，增加存貨模式的實用性。針對推導的存貨系統進行數值範例分析與敏感度分析，研究結果顯示，投資品質改善成本於改善造成各種不良率的因素能有效降低不良率且達到品質提升的效果，針對各種造成不良率因素投入品質改善成本進行改善，以效率較佳作為優先方案，依序投入資金改善品質，找出最佳存貨策略，期望將此存貨策略提供給企業做為決策參考依據，幫助企業增加利潤與提高競爭力。

Inventory for the business enterprise has been the necessarily important part. Due to the highly competitive consumer market of today, inventory management is a very important issue for the enterprise. Therefore, the enterprise must plan a suitable schedule of inventory control. The purpose of this study is to determine an optimal inventory policy for imperfect system with process quality improvement by renewal theory, this model hypothesizes an imperfect production system where the items produced are a mixture of perfect and imperfect quality. The mathematical expression for the expected objective function is derived and a solution procedure is proposed to determine the optimal policy. The study provides a manufacturing firm towards decision-making to determine the optimal production policy for imperfect production system. Numerical examples are provided to show the solution procedure, and sensitivity analysis is presented to illustrate the effects of the change of the parameter values on optimal solution. In the results of this research, the vendor invests quality improvement cost to improve product process quality. The results of this research can provide inventory managers with valuable suggestions in making the production policy.