The coupling of China's marine economy and digital economy is an important feature of Chinese-style modernization and development, which has an equally far-reaching impact on the balanced development of China's foreign trade, and is the applied meaning of Chinese-style modernization and development. Based on the panel data of 11 coastal provinces and cities along the coast of China from 2011 to 2020, this paper uses the coupling model to measure the degree of coupling coordination between the ocean economy and the digital economy. On this basis, We empirically analyse the impact of the degree of coupling coordination between the ocean economy and the digital economy on the balanced development of China's foreign trade with the double fixed effect model. The results show that the synergistic growth of the ocean economy and the digital economy is differentiated and unbalanced in coastal regions, with the Eastern Ocean Economic Circle, the Southern Ocean Economic Circle, and the Northern Ocean Economic Circle in descending order according to the development performance. Furthermore, the coupling of the digital economy with the ocean economy has a significant effect on trade quality, and the moderating effect of marine R&D expenditure and transport accessibility can more effectively promote the balanced development of China's foreign trade.