Abstract: The specific hydrological processes in wetlands determine the distribution characteristics of sediment. However, it remains unclear how the sediment particle size impact on the wetland ecological environment. In this study, we examined wetland soil in the estuary of Poyang Lake. We explored soil and water physicochemical characteristics, bacterial communities, and critical enzyme activities under different soil particle size compositions via a soil remodeling control experiment. The results indicated that the content of sand particles (0.02-2 mm) in the upper estuary wetland was 97.75%, leading to higher TN, TP, and NO3--N concentrations in the overlying water compared to other treatment groups after 120 days. Soil nutrients (SOC, TN, TP, NH₄⁺-N, NO₃^--N) showed a significantly positive correlation with specific surface area (SSA), while an inverse correlation was observed between pH and SSA. The enzyme activities related to soil carbon (β-glucosidase, catalase, polyphenol oxidase) and phosphorus (acid phosphatase) cycling increased as the soil SSA increased, while the enzyme activities related to nitrogen cycling (urease, nitrate reductase) did not show a significant correlation with soil SSA (P>0.05). Regarding bacterial communities, the relative abundance of Chloroflexi, Firmicutes, Nitrospirota, Desulfobacterota, Sva0485, MBNT15, and Latescibacterota was significantly positively correlated with soil SSA (P<0.05), while Proteobacteria, Actinobacteriota, Gemmatimonadota and Planctomycetota showed an inverse correlation with SSA. In addition, based on PLS-PM analysis, we found that the particle size composition of wetlands could affect water physical and chemical factors via altering soil physicochemical factors and the water environment via reshaping bacterial community structure and function. Therefore, soil particle composition should be considered in wetland water environment monitoring.