Abstract: The high productivity of saltmarsh vegetation in coastal wetlands plays an important role on the formation of soil carbon pool. This paper studied the biomass difference, the spatiotemporal dynamics and vertical distribution of soil carbon storage in three dominant saltmarsh plant communities, i.e., Phragmites australis, Spartina alterniflora and Scirpus mariqueter in the Chongming Dongtan wetland, in the Yangtze Estuary. The results indicated that the gross biomass in the three saltmarsh plant communities was in the order of S. alterniflora (5750.7 g·m^-2) > P. australis (4655.1 g·m^-2) > S. mariqueter (812.7 g·m^-2). The aboveground biomass was the highest in summer and autumn, and the underground biomass was the highest in winter. The soil carbon storage (0-50 cm) was the lowest in spring, gradually increased, and was the highest in winter. The annual increment of soil carbon storage decreased from the high tidal zone to the low tidal zone, and was in the order of P. australis community (711.8 g·m^-2) > S. alterniflora community (646.2 g·m^-2) > S. mariqueter community (185.3 g·m^-2) > bare mudflat (65.6 g·m^-2). The highest value was in the 25-30 cm, 10-15 cm, 30-35 cm and 30-40 cm soil layers for bare mudflat and the S. mariqueter, S. alterniflora and P. australis communities, respectively. There was a significant linear relationship between the soil carbon storage and the underground biomass in the different saltmarsh communities.