Port competition has changed from the competition between two single ports to that between two transport chains. The overlapping hinterland between two ports grows with the constant development of transport chains. A variety of subsidies offered to shippers by ports were put into practice for larger hinterland freight volume to improve port competitiveness. A study of the effects of shipper subsidies on port profits showed the following. (1) An individual port’s implementation of the subsidy strategy will expand its market share and increase its profits. (2) The competing port’s optimal response is to offer subsidies after another port has given subsidies. The optimal subsidy amounts of these two ports are the shippers’ inland transport costs. (3) Two final possibilities exist for stable states with two-port subsidy competition, that is, either both ports or neither port grants subsidies. These subsidies are associated with inland transport costs and port capacities. Considerations are given according to numerical analysis of the influence of marginal congestion cost alterations on undifferentiated positions, two-port profits, shipper surplus and social utility. The result shows that the marginal congestion costs increase will increase the profits of larger port, but will constantly lessen the shipper surplus and social utility. If both ports provide subsidies, the shipper surplus and social utility are better than those of the two ports that do not offer subsidies.

港口竞争已经从两个单一港口之间的竞争变为两个运输链之间的竞争。随着运输链的不断发展，两个港口之间重叠的腹地也随之增长。为扩大内陆货运量，已实施了港口向托运人提供的各种补贴，以提高港口竞争力。对托运人补贴对港口利润的影响的研究显示如下。（1）单个港口实施补贴策略将扩大其市场份额并增加其利润。（2）竞争港口的最佳对策是在另一个港口给予补贴之后提供补贴。这两个港口的最佳补贴金额是托运人的内陆运输成本。（3）对于具有两端口补贴竞争的稳定状态，存在两种最终可能性，即，两个港口或两个港口都不授予补贴。这些补贴与内陆运输成本和港口容量有关。根据对边际拥堵成本变动对未区分头寸，两口利润，托运人剩余和社会效用的影响的数值分析，进行了考虑。结果表明，边际拥堵成本的增加将增加较大港口的利润，但会不断减少托运人的剩余和社会效用。如果两个港口都提供补贴，则托运人的过剩和社会效用要优于两个不提供补贴的港口。根据对边际拥堵成本变动对未区分头寸，两口利润，托运人剩余和社会效用的影响的数值分析，进行了考虑。结果表明，边际拥堵成本的增加将增加较大港口的利润，但会不断减少托运人的剩余和社会效用。如果两个港口都提供补贴，则托运人的过剩和社会效用要优于两个不提供补贴的港口。根据对边际拥堵成本变动对未区分头寸，两口利润，托运人剩余和社会效用的影响的数值分析，进行了考虑。结果表明，边际拥堵成本的增加将增加较大港口的利润，但会不断减少托运人的剩余和社会效用。如果两个港口都提供补贴，则托运人的过剩和社会效用要优于两个不提供补贴的港口。