Abstract: To evaluate the carbon sequestration potential of cultivated Pacific oysters (Crassostrea gigas) in Haizhou Bay during fattening cultivation, this study calculated the total carbon sink of oyster fattening cultivation by measuring the changes in oyster carbon content before and after fattening, combined with satellite remote sensing data The results showed that during the fattening period, the individual carbon content of oysters significantly increased from 5.17 g/ind to 7.10 g/ind, but it should be noted that rapid growth during the fattening period can lead to a significant decrease in the carbon content per unit body weight of Pacific oyster. Based on satellite remote sensing data analysis, the area of oyster fattening and breeding in Haizhou Bay area has reached 1 154.97 hm², demonstrating a carbon sink function. During the fattening period, the metabolic carbon was 310.97 t and the total carbon sequestration amounted to 432.00 t, valued at 117 500 CNY. The biological carbon sink generated by one month of oyster fattening in Haizhou Bay in 2023 was equivalent to the annual carbon sink of 2 945.45 hm² of temperate forest, 5 132.67 hm² of wetland, 17 280.00 hm² of grassland, or 172.80 hm² of tropical forest. Among shellfish cultivation domestically and internationally, the individual carbon content of Pacific oysters in Haizhou Bay holds a competitive advantage, while its regional carbon sink rate is moderate. Overall analysis shows that the Haizhou Bay area still has great potential for shellfish farming carbon sink. Currently, the development of carbon sequestration in fattening cultivation in Haizhou Bay is limited by cultivation density and the lack of local supporting industries. It is suggested to increase the density of oyster raft aquaculture and develop a three-dimensional “shellfish-algae” integrated aquaculture model to sustain ecological complementary advantages.