Wetlands are gradually being lost due to climate change and excessive development. As a consequence, it has become important to muster global cooperation to conserve wetlands. Janghang Wetland, registered as a Ramsar Wetland in May 2021, is located at the estuary of the Han River and is a biodiverse wetland with a dense willow tree community. However, problems with terrestrialization of Janghang Wetland have been raised in several years. This study investigated hydrosere status and the causes through the analysis of its plant community structure. It was found that the community for Salix koreensis- Salix nipponica takes up more than 90% of the entire vegetation for willow. As a result of analyzing the MIV correlation between Salix koreensis and Salix nipponica according to the distance from waterfront, Salix koreensis flourished more as it moved away from the river. Comparison for the growth of Salix koreensis and Salix nipponica by quadrat, showed that the Salix nipponica is affected by the tidal channel. Forest tree species such as Rosa multiflora and Eleutherococcus sessiliflorus were found in the shrub layer. The amount of precipitation and water level had been decreasing for the past 5 years. In the group dominated by Salix koreensis, the NaCl of the soil was higher than the optimal level for tree growth, while the NaCl in the group dominated by Salix nipponica, tended to be very close to '0'. In Janghang Wetland, Salix nipponica community is gradually being replaced by Salix koreensis community and it causes by terrestrialization.