In the last 150 years, human activities such as fossil fuel usage and centralized agricultural schemes have resulted in the emission of large amounts of reactive nitrogen. Most of this reactive nitrogen falls to the ground via wet deposition as precipitation or dust fall. Nitrogen deposition plays a key role in the nitrogen biogeochemical cycles. Hence, quantification of nitrogen deposition in different areas is important for eco-security assessment. The Changbai Mountain region is a typical temperature forest in China; however, data regarding nitrogen deposition in this region are scarce. Investigation of nitrogen deposition in the Changbai Mountain region can provide a scientific basis for understanding nitrogen cycling in similar natural ecosystems. We conducted our present study at the Changbai Mountain Research Station of Forest Ecosystems. During 2009-2010, we collected rain and snow samples by using a rain gauge. We analyzed the concentrations of total nitrogen (TN), inorganic nitrogen (TIN), and total organic nitrogen (TON). We evaluated seasonal variations in nitrogen deposition fluxes and composition. We showed that the average nitrogen concentrations varied from month to month and were higher in winter than in summer. The amount and frequency of precipitation were the main impact factors. We observed monthly variations in TN and TIN. TON accounted for the highest proportion of TN (30.03-92.88%), whereas NO^-3 was the dominant form of TIN. The values of TN, TIN, and TON were 27.64 kg N hm^-2 a^-1, 11.05 kg N hm^-2 a^-1, and 16.59 kg N hm^-2 a^-1, respectively. The amount of nitrogen deposition varied according to the amount of precipitation and the nitrogen concentration of this precipitation. Our results indicate that nitrogen deposition in the Changbai Mountain region has reached a moderate level compared with other parts of China. However, according to the proportions of wet and dry nitrogen deposition, total nitrogen deposition has approached or even exceeded the critical load of nutrient nitrogen deposition, and this poses an environmental risk. The nitrogen deposition during the growing season (May to October) accounted for 73.20% of the annual nitrogen deposition, namely, 16.59 kg N hm^-2 a^-1, and was important for stimulating plant growth. Nitrogen deposition during the non-growing season can replenish the nutrition required by plants at the start of the next growing season and therefore should also be considered.