This paper explores that whether exist the threshold effect of financial development in Chinese marine economic growth. The result confirms that a single-threshold effect does exist and show an U-shape relation between these two variables. Financial development enhances marine economic growth only after exceeding a distinct threshold levels of initial financial sector development, which is different from Gregorio and Guidotti (1995)’s model that financial development and economic growth are positively linked. The results of marine primary industry and marine tertiary industry are basically consistent with the overall marine economy growth, showing a U-shaped relationship. On the contrary, marine secondary industry has an inverted U-shaped effect. This result is conducive to deepening financial reforms and adjusting the marine economic structure in contemporary China. Under the premise of implementing the marine development strategy, the government should also formulate relevant policies for financial support to the marine primary industry and marine tertiary industry, improve the efficiency of financial resources in the marine secondary industries to promote the sustained and rapid development of the marine economy.