In the last few decades, the progression of climate change has made people aware of the need to reduce CO2 emissions. In this study, the effect of this awareness on container transport in Northeast China is used as an empirical case study. Firstly, we propose that the freight demand index, calculated by the entropy weight TOPSIS (technique for order preference by similarity to an ideal solution) method, reflects the degree of container demand in destination cities. Then, we describe five scenarios against the background of China’s container development plan and use them to evaluate the cost and carbon emissions of container rerouting. The overall objective of the study is to assess the effects of changes in port selection on the formation of new routes and multimodal transport. The results show that carbon taxes do not significantly affect multimodal transport networks, and the impact of loading and unloading costs on the total cost is far greater than that of corresponding carbon emissions. Despite the railway transportation capacity of Dalian Port, the results show that Yingkou Port and Dandong Port will expand by 227.8% and 191.4% over 2017, respectively. Therefore, Liaoning Port Group needs to reposition its different ports.