Litter decomposition plays a major role in the cycling of nutrients in ecosystems. We have conducted a study of litter decomposition in Daebu Island. In this study, we want to assess the impact of halophyte's decomposition process on salt marsh ecosystems. Suaeda japonica is dominant in Daebu island. Salicornia europaea and Suaeda maritima, which belongs to same Chenopodiaceae, are highly developed in the island. Three species were collected, categorized according to organ and made to litter bags. The study site classified into 2 areas: around the sea and around the Shiwha lake. The Shiwha lake area divided into Suaeda japonica community, Salicornia europaea and Suaeda japonica mixed-community site. The sea area divided into Salicornia europaea and Suaeda maritima mixed-community, Suaeda maritima community, Suaeda japonica community, Suaeda japonica community with flooding. Litter bags of aboveground part were established on the soil and litter bags of belowground were buried 3cm, 10cm in depth. Then, water content, soil organic matter content, EC, salinity and pH has been measured every month. And we examined losses of weight, C, N, P, K, Ca, and Mg.