Abstract: By the methods of field survey and laboratory analysis, an investigation was conducted on the seasonal dynamics of biomass and carbon storage of Phragmites australis and Spartina alterniflora dominated vegetation belts in the Jiuduan Shoal Wetland of Yangtze Estuary, East China in 2010-2012. The organic carbon storage of the biomass (including aboveground part, underground part, and standing litter) of the two plants was the highest in autumn and the lowest in spring. The average carbon storage of the biomass of S. alterniflora per unit area (445.81 g·m^-2) was much higher than that of P. australis (285.52 g·m^-2), and the average carbon storage of the standing litter of S. alterniflora (315.28 g·m^-2) was also higher than that of P. australis (203.15 g·m^-2). However, the organic carbon storage in the surface soil (0-30 cm) under P. australis community (1048.62 g·m^-2) was almost as twice times as that under S. alterniflora community (583.33 g·m^-2). Overall, the carbon accumulation ability of P. australis community (3212.96 g·m^-2) was stronger than that of the S. alterniflora community (2730.42 g·m^-2). Therefore, it is of significance to protect the P. australis community in terms of carbon sequestration at the salt marsh.