The modern society faces a major challenge of environmental protection and achieving sustainable development due to the rapid expansion of the world economy and sustained population growth. This research focuses on the degree of synchronization between marine ecology and the economy. The objective of this study is to address this issue. The aim of this study was to determine the level of synchronization between marine ecology and the economy in nine coastal provinces of China from 2017 to 2022. This study examined the coordination between marine ecology and economy, using sustainable development theory and systems theory. The main focus was on the degree of synchronization between marine ecology and the economy. The study employed the coupling coordination model to evaluate the degree of coordination between marine ecology and economy selected for the study. The study analyzed differences in the degree of coordination and overall trends over time, as well as factors affecting the coordination of marine ecology and the economy. Kernel density and barrier degree models were used for the analysis. Finally, the study examined the key factors that affect the coordination of marine ecology and the economy in these regions using the barrier degree model. The evaluation index for coastal areas decreased from 0.179 to 0.153, indicating a decline in the marine environment. The eastern and southern marine economic circles exhibited a fluctuating upward trend. To enhance coordination between the economy and the ecological environment, this study recommends that coastal provinces prioritize environmental protection, adopt green development principles, increase investment in science and technology, and accelerate the transformation of marine science and technology.