The ecophysiological responses of fine roots to nitrogen deposition will significantly influence the productivity and carbon sequestration of forest ecosystems. Currently, there is large quantity of researches on the responses of fine roots to nitrogen deposition, but there are still some controversies. In the present study,a simulated nitrogen deposition experiment was conducted to investigate the impact of nitrogen deposition on fine root ecophysiological traits of 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings. According to the ambient nitrogen deposition, three nitrogen addition levels were set:control (CT, 0 kg N hm^-2 a^-1), low nitrogen (LN, 40 kg N hm^-2 a^-1), and high nitrogen (HN, 80 kg N hm^-2 a^-1). Ingrowth core method and soil core method were applied to measure fine root biomass, morphology (specific root length and specific root surface area, root tissue density), stoichiometry (C, N, P, C/N, C/P, N/P), and metabolic characteristics (specific root respiration rate, soluble sugar, starch, nonstructural carbohydrates) after one year of simulated nitrogen deposition. The results showed that:(1) Nitrogen addition significantly reduced Chinese fir fine root biomass, but significantly increased specific root length and specific root surface area, especially for roots of the 0-1 mm diameter class. While nitrogen addition had no significant effect on fine root tissue density, HN treatment did decrease fine root tissue density of the 0-1 mm roots. Compared with the 1-2 mm roots, the 0-1 mm roots were more flexible to change in terms of root biomass, specific root length, specific root surface area. (2) Nitrogen addition significantly reduced C concentration and decreased C/N and C/P in fine roots, N concentration and the N/P ratio in fine roots of 1-2 mm were significantly increased in HN treatment, while in LN treatment, P concentration was significantly increased and N/P significantly decreased in fine root of 1-2 mm. There seemed an interesting phenomenon that P absorption of fine roots was improved only under low level nitrogen addition. Compared with the 1-2 mm roots, the 0-1 mm roots had more conservative concentrations of both N and P.(3)Under nitrogen addition, specific fine root respiration rate had no significant change. Soluble sugar concentration in fine roots increased significantly with nitrogen addition, but the concentrations of starch and nonstructural carbohydrate were significantly reduced. In conclusion, the results showed that the C allocation to build fine roots decreased with nitrogen addition and it might decrease soil C sequestration through fine root turnover. Compared with the 1-2 mm roots, the 0-1 mm roots seemed more flexible to alter their morphology (specific length and surface area), while more conservative in N and P concentrations in order to maintain the ecophysiological activities in fine roots. Under nitrogen addition, specific root respiration was unchanged, but the total nonstructural carbohydrate in fine roots significantly decreased and more starch was converted into soluble sugar, which implied that fine roots under nitrogen addition might subject to carbohydrate limitation.