The comprehensive evaluation system for competitiveness of port cities is established from four aspects of economy, society, environment and port resources. The competitive powers of three major coastal port cites in Jiangsu Province, Yancheng, Lianyungang and Nantong, are evaluated by using the principal component analysis, and they are comparatively analyzed with 12 coastal port cities first opened in China at different levels. The results show that the three major cities in Jiangsu Province rank in the middle and lower level of the sample cities, and they have large differences with the leading cities. Finally, some policy recommendations are proposed to improve the competitiveness of coastal port cities based on the construction of “One Belt and One Road”.