本研究以航運成本與貨物存貨成本最小化之雙目標，探討航商定期多港靠泊貨櫃航線的船型與頻次決策。航運成本函數含船舶時間成本、燃油成本與港 埠成本，貨物存貨成本函數含等待時間成本與航運時間成本。本研究並推導航運成本與貨物存貨成本的數學關係式，求得雙目標的可行解與柏拉圖最佳解，並以圖示顯示在目標值空間上，於各種情境下進行決策之分析方法。研究結果不僅可得不同存貨成本水準下的最適船型，亦顯示貨物存貨成本、船舶規模經濟性與航速在決策中的影響。此外，本研究並推導船型決策臨界點隨貨物流量變動的數學關係式，並顯示隨貨物流量增加傾向使用最小航運成本較小船型的趨勢。最後，以一越太平洋航線為例驗證理論推導結果。

On this study, we formulated a two-objective model by minimizing both shipping costs and inventory costs to decide ship size and sailing frequency for container liners. First, shipping and inventory cost functions are formulated for a multi- port calling route. Shipping costs include capital and operating cost, fuel cost, and port charges, while inventory costs include waiting time cost and shipping time cost. Furthermore, we derived a trade-off equation between shipping costs and inventory costs that shows all solutions of ship size and sailing frequency, and identified that it is a hyperbola function, which could be shown in objective value space. Accordingly, Pareto optimal solutions of the two-objective model are then determined, and ship size and sailing frequency decision analysis can be made. The optimum ship size for each level of inventory cost is shown and the effects of inventory costs, economies of ship size, and service speed on decision are also illustrated. Besides, we derived the relationship between the optimum ship size and container flow, and showed that the optimum ship size tended to be the ship with the minimum shipping cost as container flow increases. Finally, a case study regarding Transpacific Northwest Service justified the theoretical findings.