Abstract: The interaction between sea and land is the key to coastal eco-hydrological study. The gradients of shallow groundwater and brackish water in sediments are critical to coastal eco-hydrological vulnerability. The desalination of brackish water is driven by the joint action of groundwater dynamics, hydrogeochemical differentiation and tidal process. The research progress on the mechanism of brackish water desalination in delta wetland was discussed in this paper. In order to restore the hydrological conditions, it is required to take effective protective measures in accordance with the mechanism of the brackish water desalination and the movement of shallow groundwater.