Under the great changes unseen in a century, ASEAN, the fourth trading partner of China's aquatic products export in 2010, has evolved into the first place since 2020. To take precise measures to consolidate and develop the international competitiveness of China's aquatic products, based on the data of UNcomtrade from 2010 to 2022, this study first analyzes the fluctuations of China's aquatic products export to ASEAN and the economic and trade relations. Then the CMS second-order decomposition effect model is used to measure the dynamic effect of the driving factors of fluctuation of China's aquatic products exports to ASEAN. The results show that under the background of the Belt and Road, the effect of ASEAN import demand growth on China's aquatic products exports has a positive effect of continuous growth in the three periods, but the effect of product competitiveness is negative in the three periods. Therefore, based on the background of the new development pattern, it is proposed to make full use of the market effect of The Belt and Road to strengthen international cooperation, give full play to China's digital application advantages, optimize the structure of China's aquatic products, improve the dynamic management ability of China's aquatic products in the international market, and consolidate and enhance the core competitiveness of China's aquatic products in the international market.