The excessive emission of greenhouse gases results in global warming, and CO_2 contributes to this process by about 60%. Shellfish culture has effect of carbon deposition which was calculated and evaluated by the 10 year average yield of fishing shellfish and culturing shellfish production from 2001 year to 2010 year based on China Fishery Statistics Yearbook. The unit area carbon deposition capacity of oyster, clam, scallop and mussel was calculated and compared with the carbon deposition capacity of forests and coral reefs. Analysis shows that the total yield of shellfish is stable and more than 110 million tons with an increasing trend and the mariculture shellfish is account for about 87.34%. The total carbon deposition of shellfish aquaculture and capture and the amount of carbon deposition of the mariculture shellfish are approximately 585.7 and 511.5 thousand tons per year, respectively, which are equivalent to about 1222.8 and 1067.8 thousand hectares afforestation for carbon deposition and can reduce the increasing amount of CO_2 in the atmosphere by approximately 0.0125 % and 0.0109 % respectively. Carbon deposition rates of oyster, clam, scallop and mussel are 1.573, 0.388, 0.301 and 1.039 t/(ha? a), respectively. The carbon deposition rates of oyster and mussel with consumption of economic value are higher than the forest (0.479 tC/(ha? a)), but lower than the coral reefs (1.8 t/(ha? a)). The effect of using the shellfish for carbon deposition is superior to capture and archive CO_2 directly into deep sea by carbon capture and storage engineering. Freshwater culture shellfish and mariculture shellfish can create carbon credit opportunities 2.684 million yuan and 127.112 million yuan per year respectively in China.