Abstract: To elucidate the effects of nitrogen (N) and phosphorus (P) input ratios on soil ecological functions in coastal Phragmites australis wetland, we conducted a long-term (9-year) study using the N and P nutrient addition control platform in the Yellow River Delta coastal wetlands. We examined the impacts of three N:P input ratios (5:1, 15:1, and 45:1) on soil physicochemical properties, enzyme activities, and the composition and stability of soil aggregates. The results showed that under the 5:1 N:P input ratio, the soil total phosphorus content at 0-10 cm depth was significantly higher than that of other treatment groups, but the contents of NH₄⁺-N and NO₃⁻-N of soil were relatively stable, and did not show significant differences from the control group. Regarding soil enzyme activities, long-term N and P inputs significantly reduced urease and sucrase activities in the 0-10 cm soil layer, while alkaline phosphatase activity remained largely unchanged. As soil depth increased, the proportion of microaggregates in the soil aggregate composition also increased. Although changes in the N:P input ratio affected soil aggregate stability, the overall differences compared to the control group were minimal. Soil enzyme activity showed a significant positive correlation with NH₄⁺-N and NO₃⁻-N content, whereas conductivity was negatively correlated with microaggregate content. The study demonstrated that variations in N:P input ratios significantly influence the physicochemical properties, enzyme activities, and aggregate composition and stability of coastal reed wetland soils. Long-term excessive input of either N or P can inhibit soil enzyme activity, alter soil aggregate size composition and stability, and ultimately impact wetland soil ecological functions. These findings provide crucial insights for the ecological restoration and management of coastal Phragmites australis wetlands.