Abstract: Under the context of the spatial distribution characteristics and carbon effects of oyster reefs in Haimen, Jiangsu, we explored the influence of oyster reefs in Haimen, on marine carbon sequestration capacity. A carbon storage estimation model for oyster reefs was established to analyze their spatial distribution patterns and the spatiotemporal variations in carbon storage, as well as to estimate their carbon sequestration potential. Results indicate that oyster reef carbon storage and distribution were influenced by multiple factors in significant spatial heterogeneity. Specifically, the distributions of total carbon and inorganic carbon content across layers were relatively uneven, while organic carbon content showed a more uniform distribution. The organic carbon content in the substrate sediments of oyster reefs was relatively balanced, although overall sediment composition fluctuated considerably, exhibiting a vertical trend of decrease-increase-decrease in boreholes. Based on carbon storage variation methods and field monitoring data, the estimated carbon sequestration capacity of oyster reefs in Jiangsu Haimen was 1.37 kg/m². Oyster reefs significantly enhanced the marine carbon sequestration through three key processes: calcification, biological assimilation, and biodeposition. Among them, the carbon sequestered via calcification was particularly prominent, offering novel perspectives and methodologies for improving carbon sink capacity in marine ecosystems.