Abstract: Coastal wetlands have important ecological and environmental values. The core area of the Yancheng National Natural Reserve, which is an area in need of 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, and there is no 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 RTK. For the data table, several methods were used to process the data, including seasonal comparisons, cumulative changes over the years, profile changes, slope changes, and continuous changes in site elevation. Comparison of seasonal change shows the trend and rate of change in different seasons, interannual change reflects the amount of cumulative change, profile change and slope change reflect variation in the morphology of the profile in which the monitoring stations are located, and continuous changes in site elevation show fluctuations in the topography over time. Data from these 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, with cumulative values of tidal flat bed lowering ranging from 0.78 m to 1.30 m over the four-year period, and rates of erosion lowering ranging from 0.20 to 0.32 m/a. The fitting of the long-term monitoring values shows the longterm trend of continuous erosion and the mode of phase change characteristics. However, the southern tidal flat shows the dynamics of siltation, erosion, and re-silting, and in general siltation still dominates in the area. These monitoring data record the process and scale of tidal flat bed change, reveal the process of erosion of the coast, and help to verify the numerical simulation results. These are important for the management of the wetland reserve and the development of strategies to cope with erosion.