Abstract: The dynamics of nitrogen(N)in the atmospheric wet deposition in typical wetland ecosystem of Sanjiang plain was studied from July 2004 to June 2005,and its ecological ef ects were also analyzed. The results show that there are significant differences among monthly average N concentrations,and the seasonality is evident. The reasons are mainly correlated with human activities,precipitation intensity and frequency,wind direction,geographical location and NO_x natural emission. The total inor ganic nitrogen(TIN)is the main body of the total nitrogen(TN)in wet deposition(51.38%~98.96%),and the ammonium nitrogen(NH₄⁺-N),nitrate nitrogen(NO₃^--N),especially NH₄⁺ N,are the main body of TIN. The path of precipitation synoptic system,to a greatextent,affects the composition of N in wet deposition. The precipitation only has faintish negative correla tions with N concentrations(p>0.05),but the NH₄⁺-N has significant positive correlations with NO₃^--N and TON(p<0.05), and they might have homologue. The better correlation between NH₄⁺-N and NO₃^--N is mainly related with their reactions in liquidoid. The growing season is the important phase of N deposition in a year,its deposition amount is 1.84 folds of that in non growing season,and their proportions are 64.78% and 35.22%,respectively. The deposition amounts of N in growing season are much higher than those in non growing season except nitrite nitrogen(NO₂^--N)The total N deposition amount in a year is 7.57 kg/hm²,and TIN/TON ratio is 5.47. These show that TIN is the main deposit ion body and its proportion is 84.56% Moreover, NH₄⁺-N and NO₃^--N are the main body of TIN,and their proportions are 52.55% and 30.03%,respectively Further analysis indicates that N is the limited factor that affects the growth of plant. The N deposition in growing season has direct ecological signification which might stimulate the growth of plant,but in non growing season,the N deposition has indirect ecological signification which can greatly supplement the nutrient in initial growth stage of plant in the second year.Anyhow the ecological func tions can not be neglected. In recent years,the decrease of N deposit ion amount in wetland ecosystem might be the important cause which induces the wetland degradation,nor can its ecological effects be neglected.