In the process of nitrogen cycling in wetland ecosystem, there is a direct relationship between the supply and availability of wetland soil nutrients and nitrogen content. In this study, the nitrogen content which existing in the surface soil of the plant community under the natural succession of the Caohai Wetland in Guizhou Province was selected as the research object. The content of nitrate nitrogen(NO3--N), ammonium nitrogen(NH4+-N), available nitrogen (AN) and total nitrogen (TN) in four kinds of phytocoenosium as well as the spatial distribution characteristics of wetland soil nitrogen under different soil aggregate particle sizes were studied. The surface soil of four typical wetland plant communities (i.e. Goosegrass, Leesgrass, Elsholtzia and Phragmites) were collected, and the physical and chemical properties of each layer of the soil were measured. The results showed that: (1) The distribution trend of soil cation exchange capacity (CEC) and TN content in each plant community was basically the same. The contents of CEC, AN and TN in the soil of Phragmites communis were the highest, which were 362.96±61.48 mg kg-1, 22.17±2.02 mg kg-1 and 0.35±0.18 g kg-1, respectively; (2) The contents of AN and TN in soil aggregates with different particle sizes in each plant community had no significant difference (p>0.05). In the Phragmites community, the contents of NO3--N in the soil aggregates with different size were the lowest; in the Leesgrass community, the contents of NH4+-N in the soil aggregates with different sizes were significantly different (p<0.05). In August, plants were in the vigorous growth period, while Caohai was in the wet period. The distribution of nitrogen contents in the surface of the plant community was affected by plant species, its own litter, rainfall, topography, microbial activities, organic matter, and growth period et al. factors. As a result, soil nitrification was inhibited or promoted, and the final manifestation was that the distribution of ammonium nitrogen and nitrate nitrogen in each plant community was significantly different. The nitrogen content of wetland surface soil was also affected by the external nitrogen input in the water body and the distribution structure of nitrogen itself in the natural soil. Therefore, the nitrogen content of various plant communities was not consistent, especially the content of TN in the soil.