Abstract: Since the implementation of carbon peak and carbon neutral targets, the green and low carbon has become the theme of the era. In order to scientifically explore the carbon sink capacity of Guangxi’s mariculture shellfish, the related production and carbon sink capacity from 2013 to 2022 was assessed. Results show that the average annual production of shellfish in Guangxi over this period is 93.85×10⁴ t, accounting for 6.70% of the national shellfish, and the proportion of shellfish production in Guangxi to the national shellfish production is increasing year by year. From the perspective of carbon sink, the annual average of estimated carbon sinks of shellfish aquaculture in Guangxi is about 7.62×10⁴ t, following the order of oysters, clams, snails, mussels, scallops, ark clam, and razor clams from high to low. Among them, oysters made the largest contribution, accounting for 61.55% of the carbon sink of shellfish, and were the main economic shellfish species in Guangxi. The next was clams, accounting for 29.53% of the carbon sink. From the perspective of carbon sink efficiency per unit area, mussels had the highest carbon sink efficiency, reaching 8.49 t/hm² and the following was oysters and clams, with 2.93 t/hm² and 2.57 t/hm², respectively. The mariculture shellfish in Guangxi Province is a carbon sink with no feeding, and the potential of carbon sink and the economic value of emission reduction are huge. In addition, in order to help the development of China’s carbon sink fishery, Guangxi should accelerate the construction of a trading platform for fishery carbon sinks and a carbon balance model for major economic shellfish species, and explore the migration and conversion laws of shellfish for carbon, nitrogen and phosphorus, etc. High carbon sequestration is a key characteristic of shellfish in the future and it will become an important way for the green, low-carbon and sustainable development of Guangxi’s marine aquaculture contributing to the country’s “double carbon” goal.