Abstract: To detect the carbon contents of common bivalve mollusks in the South China Sea and evaluate the carbon sequestration capacity of bivalve mollusks cultivated in Guangdong, Guangxi and Hainan, this study measured the carbon contents in the shells and soft tissues of 21 common tropical bivalve mollusks. Additionally, based on the carbon contents of these mollusks, a statistical analysis was conducted on the carbon sequestration capacity of bivalve mollusks cultivated in Guangdong, Guangxi and Hainan in 2022. The results showed that the carbon contents of soft tissues in 21 bivalve mollusks ranged from 31.33%～43.20%, with the highest being observed in Sinonovacula constricta and the lowest in Spondylus aurantius; the carbon content of their shells ranged from 11.32% to 14.35%, with the highest in Perna viridis and the lowest in Mimachlamys nobilis; the carbon content of the whole body wet weight ranged from 7.10% to 11.48%, with the lowest content found in Atrina pectinata and the highest in Sinonovacula constricta. The total carbon sequestration capacities of bivalve mollusks cultivated in Guangdong, Guangxi and Hainan provinces in 2022 were 145, 936, 104, 645 and 164 t, respectively; the carbon sequestration capacities per unit area in these provinces were 2.78, 3.14 and 0.15 t·hm⁻², respectively.