While the marine economy is developing rapidly, it is necessary to keep a watchful eye on associated security risks and their prevention in the process of marine economic development. This study takes the marine economic system as the core to comprehensively measure the marine economic security diffusion index and the composite index of China and the three major marine economic circles from 2007 to 2018. Furthermore, it presents the leading analysis of the leading composite index for realizing real-time monitoring using climate analysis and statistical analysis methods. The results show that the leading diffusion index of marine economic security can effectively reflect the turning point, and the leading composite index can better monitor the trend. In the future, China's marine economic security will begin to shift from the stage of rising fluctuations to the stage of dynamic adjustment, which also reflects the realistic problem of insufficient endogenous power. Compared with the synchronous composite index, the leading composite index of marine economic security has a one-year leading advantage from 2014 to 2018 in China. In addition, the impulse response results indicate that the leading composite index of marine economic security in the whole country and the three major marine economic circles has a continuous effect on the synchronous composite index. By establishing a marine economic security climate measurement system, to a certain extent, this study fills some gaps in the field of marine economic security climate monitoring in China and has great practical significance.