Spatial distribution of nitrogen in the soil, biomass and nitrogen contents of Typha latifolia community, Polygonum hydropiper community, Juncus effuses community and Phragmites communis community in the Zhucao river mouth wetland into Daxi Reservoir in Liyang City, Jiangsu Province were studied. Significant differences of aboveground biomass, belowground biomass and nitrogen contents of four plants were found. Soil loss on ignition (LOI), total nitrogen (TN) and nitrate nitrogen (NO₃^--N) concentrations showed decreasing trend on the vertical distribution with increasing depth. Ammonium nitrogen (NH₄⁺-N) concentrations in soil profiles decreased first, and then increased. Soil nitrogen concentrations of the four plant communities were different, but most of them were higher than the control, and organic nitrogen was the main form, indicating that the wetland had a certain nitrogen storage capacity and different plant communities affected the distribution of nitrogen. The correlations between LOI and total nitrogen, ammonium nitrogen, nitrate nitrogen were significant. Inorganic nitrogen constituted only a small proportion (1.41%), which indicated that the nitrogen mainly presented in the organic form. However, there was nearly no correlation between biomass, nitrogen contents of four types of plant and nitrogen concentrations of each soil layer. This indicated that soil nitrogen contents were affected not only by the form of plant growth, but also by the plant root zone environment, the number and activity of microorganisms.