The study of the carrying capacity of China's marine composite system is of great significance to the development of marine standardization. Based on the Environmental Kuznets Curve (EKC) hypothesis, the use of variable fuzzy identification algorithms, combined with relevant research to construct a carrying capacity index and evaluation system to evaluate the carrying capacity of China's marine environmental resource and economic system from 2006 to 2014. The coordinated development model measures the coordinated development of the carrying capacity of the composite system. Finally, we used gray relational analysis to measure the factors influencing the carrying capacity in order to provide a reference for the sustainable development of the marine composite system in China. The results of the study indicate that: (1) the time series of China's marine composite system's carrying capacity shows an increasing trend; the carrying capacities of Tianjin, Shanghai, and Hainan, the pattern of the "three pillars" in the north and south, are higher in space than other locations, but the carrying capacities of Hebei and Guangxi are relatively low; (2) the coordinated development of the carrying capacity also showed positive development, but the differences among regions were large, with higher coordinations in Hainan, Shandong, Shanghai and Tianjin than other locations.The development of most other regions needs to be improved. (3) The scale of the marine economy and industrial structure, environmental governance, and richness of resources affect the changes in carrying capacity of the marine economy, environment, and resources.