Abstract: Coastal wetlands have important ecological and environmental values. The core area of the Yancheng National Natural Reserve needs urgent protection. The reserve has been subjected to erosion since 2012, and the edge of the salt marsh has been retreating and tidal flat bed has been deepening. However, there is no proven method on how to carry out seasonal and long-term monitoring on the tidal flats in the reserve, nor the systematic accumulation of data and information. The rod-type surface elevation monitoring system is a widely used wetland elevation monitoring system. Based on the characteristics of tidal flats dynamics, we improved the system and applied it to the tidal flats of the coastal wetlands. Monitoring stations were established in five typical shore beaches, and erosion and siltation monitoring has been carried out seasonally for more than four years. On this basis, a data table of surface elevation changes was formed by combining the absolute elevations measured by Real-Time Kinematic positioning (RTK). The data table was processed in several methods, including seasonal comparisons, cumulative changes over the years, profile changes, slope changes, and continuous changes in site elevation. Results show that the seasonal and interannual changes in trend and rate changes reflect the amount of cumulative change; profile change and slope changes indicate morphological variation of the profile where monitoring stations situated; and the continuous changes in site elevation show fluctuations in topography over time. Data from the monitoring stations combined with beach surveys reveal the erosion history on the northern side of the reserve and the erosion-siltation changes on the southern side. The monitoring data in the north indicate that the shoreline has been eroding overall, and the cumulative values of tidal flatbed were lowered from 0.78 to 1.30 m in the four-year period of monitoring, and rates of erosion was decreased from 0.20 to 0.32 m/a. The fitting of the monitoring showed the longterm trend of continuous erosion and the mode of phase change. However, the southern tidal flat showed the dynamics of siltation, erosion, and re-silting, and in general siltation still dominated in the area. The monitoring data record the process and scale of tidal flatbed change, reveal the process of erosion of the coast, and help to verify the numerical simulation results, which is important for the management of the wetland reserve and the development of strategies against erosion.