Nitrogen (N) is one of the most important element in plant growth and an important part of the global ecosystem substances circulation. Organic N is both the main form of soil N and pool of mineral N. Soil organic N plays an important role in soil fertility, N cycling and environmental protection. Usually, the concentration and distribution of soil organic N mainly affected by soil types, soil level, rhizospheric environment, fertility and farming conditions, etc, and the chemical forms and status of soil organic N is the important factor affecting the availability of soil N. Currently, researchers have focused more on effect of different land use systems on changes of soil organic N fractions, dissolved organic N, particulate organic N and microbial biomass N, as well as effect of different fertilization and irrigation approaches on concentrations and composition of organic N fractions by using the Bremner's method to separate soil organic N fractions. Combined with filed investigation, five types of soil samples in the lower reaches of Heihe river wetland were collected, and the organic N fractions were studied using the Bremner's method, the results showed that acidolysable N was the dominant fraction of organic N in all the soil samples (0-50 cm soil layer), and the proportion of acidolysable N to total N was from 71.04% to 81.79%. The concentrations of acidolysable N, non-acidolysable N and acidolysable N fractions (ammonia N, amino acid N, amino sugar N) of Peat soil, Boggy soil, Meadow soil, Subalpine meadow soil decreased, but increased in the Aeolian sandy soil generally with soil depth in the profile. Furthermore, the proportions of acidolysable N and acidolysable N fractions (ammonia N, amino acid N, amino sugar N) to total N of all the soil samples generally decreased with soil depth in the profile distribution, while the proportion of non-acidolysable N to total N generally increased with soil depth in the profile distribution. The concentration of acidolysable unknown N and the proportion to total N of all the soil samples did not show any specific characteristics. In addition, in the same soil layer (0-30 cm), the concentrations of acidolysable N fractions and the proportions to total N varied as the followings: amino acid N > ammonia N > unknown N > amino sugar N; However, in 30-50 cm soil layer, the concentrations of acidolysable N fractions and the proportions to total N of the soil did not show any typic characteristics. Besides, the soil organic N fractions in the surface soil (0-10 cm) changed obviously along with the soil desiccation and desertification in the lower reaches of the Heihe River wetland, and the soil ammonia N of soil was the most sensitive one to the ecological environment factors.