Atmospheric nitrogen (N) deposition, as both a component of acid deposition and a nutrient source, is of increasing interest. Most research on N deposition mainly focuses on sensitive natural ecosystems such as forests and in developed countries. Information on N deposition in important ecosystems such as the Qinghai-Tibet Plateau is scarce. Although we might expect less impact from anthropogenic deposition compared with other regions of China, the ecological environment there is fragile. A study of atmospheric N input in this region would not only indicate N deposition in remote areas of high altitude, but also provide a scientific basis for understanding the N cycle in such natural ecosystems. The research was carried out at the Ecology Research Institute, Tibet Agricultural and Animal Husbandry College, in a typical forest ecosystem of southeast Tibet. Rain and snow samples were collected and analysed and N concentration and deposition calculated for 2005 and 2006. Annual wet deposition of inorganic N averaged 2.36 kg/ (hm2 a). Volume-weighted concentrations of NH+4-N and NO-3-N were 0.36 mg/L and 0.10mg/L, respectively, and varied throughout the year. Higher values of N concentration in rain were found in winter and spring, while lower values were found in summer and autumn.Both the NH+4-N and NO-3-N deposition significantly decreased with the increased precipitation (p (NH+4-N) = 0.006, p (NO-3-N) = 0.019), and N concentrations significantly increased with precipitation, fitting a power equation (p﹤0.05). N deposition was highest; the lowest value was found in winter (only 2%-3% of total annual deposition). NH+4-N was the dominant species in wet deposition, comprising 81.1% of total wet inorganic N deposition.