In order to understand the physical and chemical properties of sediment oxide layer in surface flow constructed wetland of Yanlong Lake, Yancheng City, and to explore its influence on the release process of nitrogen, phosphorus and organic matter from sediment, indoor static columnar tests were carried out on the basis of determining the physical and chemical properties of sediment. The results showed that after long-term operation, the surface flow constructed wetland of Yanlong Lake formed oxidized layer with thickness of 1cm, brown-yellow, no obvious odor, low water content, high TP content, low TOC and TN contents on the surface of sediment. The oxidation layer has a significant effect on the release characteristics of pollutants in sediment(P<0. 05), and has a positive effect on the control of endogenous pollution. The average concentration of TN, NH₃-N and COD in the overlying water of the non-oxidized layer test group was 9. 5%, 30. 8% and 3. 5% higher than that of the oxidized layer test group, respectively. In the actual management of wetlands, it is not appropriate to dredge wetlands. If dredging, the dredging depth should reach the healthy layer.