Soil enzyme plays an active role in the material circulation and energy flow of soil biochemical process. This article deals with the seasonal change of soil enzyme activities of phosphatase, urease and catalase in Phragmites communis and Spartina alterniflora communities in Dafeng coastal wetland after carrying out the eco-engineering with hydro-geomorphological modification. Meanwhile the relationship between the soil enzymic activitives and physical-chemical factors is discussed by correlation analysis. The results showed ：(1) The seasonal variation curves of the soil phosphatase activity in two communities were all “single peak curves”, while the soil catalase activity in two communities were all “single valley curves”. The maximal soil phosphatase activity values and the minimum soil catalase activity values of both communities all appeared in summer (August). However, the soil urease activities of two communities changed erratically within a year. (2) The result from the correlation analysis showed there was significant positive correlation between the soil phosphatase activities and soil salinity, community biomass in Spartina alterniflora communities, while the correlation analysis between the soil catalase activities and two physical-chemical factors was vice versa. In Phragmites communis communities, the soil phosphatase activities had a significant positive correlation with organic matter and available P, while the soil catalase activities was vice versa. There was no correlation between the soil urease activities and all physical-chemical factors in both communities.(3) Path analysis between soil enzyme activities and soil phy-chemical factors showed that soil enzyme activities were the result of interactions among soil phy-chemical factors,and each factor acted differently in the two communities. In the S.alterniflora community, soil phy-chemical factors affecting phosphatase activity, urease activity and catalase activity decreased in the orders of soil salinity＞available K＞available P＞O.M.＞ammoniacal N, O.M. ＞available K＞available P＞soil salinity＞ammoniacal N and available K＞soil salinity＞O.M. ＞available P＞ammoniacal N. In the P.communis community, the orders were available P＞soil salinity＞O.M.＞ammoniacal N＞available K, O.M.＞available K＞soil salinity＞ammoniacal N＞available P and ammoniacal N＞available K＞soil salinity＞available P＞O.M..(4) The eco-engineering of hydro-geomorphological modification meliorated the coastal wetland soil to some extent, and it was propitious to substitute Phragmites communis community for Spartina alterniflora community.