Abstract: Wetlands are active storage places of mercury. It is of great significance to research the accumulation of mercury in wetlands to understand the biogeochemical cycle of mercury and the ecological impacts on the wetlands. Investigating the mercury accumulation in sediments of Chongming Wetland can provide a foundation for future research on the biogeochemical cycle of mercury in wetlands and environmental protection of wetlands. The contents of mercury, iron, manganese, and organic matter, as well as the grain sizes of three cores from the high, medium flat and the front of medium tidal flat vegetation zonesin Chongming Wetland were investigated. The distribution characteristics of mercury in the sediments were analyzed. The mercury content in the sediments of Chongming Wetland ranged from 0.015-0.315 mg/kg. The index of geoaccumulation I_geo was used to evaluate the enrichment and pollution of mercury in the sediments. The analytical results show that the mercury accumulationin Chongming Wetland reached the slightly-polluted level. To some extent, thereis an enrichment of mercury. By means of correlation analysis, environmental factors such as organic matter content, iron, manganese and grain size affecting Hg concentration variation in the sediments were explored, suggesting that organic matter, iron and manganese play an important role in mercury accumulation in tidal flat sediments. The grain size of sediment is not the main factor in the geochemical cycle of mercury in tidal flat sediments.