The marine economy is a vital component of boosting the high-quality development of the Chinese economy. According to the concept of high-quality development, we construct the evaluation indicator system to measure the level of high-quality development of the marine economy by means of the combined empowerment method. We explore the coupling coordination relationship and evolution trend with the coupling coordination degree model, and finally, we analyze the regional differences using the Dagum Gini coefficient. The results show that, (1) from the perspective of time, China’s marine economic high-quality development index has been steadily improving, but there is still great potential for progress. From the perspective of spatial characteristics, the eastern marine economic circle has the best level of high-quality economic development. (2) From 2012 to 2022, the coupling coordination degree of high-quality development of the marine economy experienced five stages, from the verge of disorder to finally stepping into the good coupling coordination stage. (3) The overall difference in the marine economy is gradually narrowing. Among the three major marine economic circles, the southern marine economic circle has the largest internal discrepancy, which has become an important factor affecting the high-quality development of the marine economy. The above research results helped relevant decision-making departments to deeply understand the status quo and outstanding contradictions of the high-quality development of the marine economy in China.