The response of soil enzyme activity of freshwater marsh, microbial biomass carbon (MBC) ，dissolved organic carbon (DOC) and aboveground biomass to water gradient were studied by Carex lasiocarpa pot culture experiment. And the relationship between soil enzyme activity and MBC, DOC, aboveground biomass were discussed. The water gradients were W1:15cm, W2: -5cm, W3: -5-5cm and W4: submerge. The results indicated that the activities of acid phosphatase, invertase, urease and those activities were decreased with the increase of water content，while Catalase activity was increased with water content increasing. And Drying-Wetting Alternation（W3）increased these soil enzyme activities, comparing with W1. MBC content was in the order of W3>W1>W2>W4 and the activities of invertase, urease and catalase were significantly positively correlated with MBC (p<0.05). DOC content was in the order of W4>W1>W3>W2 and the activities of urease and acid phosphatase were most significantly negatively correlated with DOC (p<0.01). And MBC more closely related to soil enzyme activities. In addition, Drying-Wetting Alternation promoted the growth of Carex lasiocarpa. When the water submerged plant, the growth of Carex lasiocarpa was significantly inhibited. The aboveground biomass of Carex lasiocarpa was positively related to soil enzyme activity. And there were close relationship between the activities of invertase, urease and catalase and the growth situation of Carex lasiocarpa.