Soil samples were collected from natural vegetation zones and farms in the Yancheng coastal wetland, Jiangsu province. The activities of soil enzymes (urease, invertase, catalase, alkaline phosphatase) were determined and the influence of salt marsh vegetation communities and soil physico-chemical properties on soil enzyme activities was discussed. The results showed that the activities of the soil enzymes in the natural vegetation zones were higher than those in the mudflat without vegetation and there were significant differences among different vegetation zones. However, the activities of soil enzymes in farms were higher than those in the natural vegetation zones and these enzyme activities were represented in the order as: Glycine max field > Gossypium hirsutum field > Zea mays field > Spartina alterniflora flat > Imperata cylindrica var. major flat > Suaeda salsa flat > mudflat. Significant positive correlations were found among different soil enzymes and among enzyme activities, soil organic carbon and total nitrogen, but there were negative correlations among enzyme activities and soil salinity and pH value. Soil fertility and enzyme activities were shown to be improved along the development of vegetation.