Abstract: To explore the distribution pattern and formation mechanism of salt in the stratum of supratidal saltmarsh system, the coastal saltmarsh wetland in Yancheng, Jiangsu Province, was considered in this study. The spatial distribution of soil porewater salinity was obtained through resistivity measurement and soil sample analysis, and the corresponding relationship with ecogeomorphology was further revealed. As a result, the groundwater salinity below the depth of 10 m is relatively high and uniformly distributed, while shallow porewater above 5 m depth is significantly desalinated. The degree of porewater desalination is related to the characteristics of zonal ecogeomorphology. Salinity of shallow porewater in the near-creek area is close to that of seawater. However, the shallow stratum underneath the crab hole area and Spartina alterniflora area has much lower salinity, with the former presenting a larger spatial scale. The short period tidal process only affects the localized salinity near the tidal creek. The crab holes significantly promote the infiltration of rainwater and its desalination effect, and contribute to near-surface evaporation and salt accumulation, increasing the vertical difference of shallow soil water salinity. The root preferential flow and evaporation inhibition caused by vegetation growth effectively reduce the salinity level of surface soil.