Abstract: 【Objective】Study the effects of elevated nitrogen deposition on soil microbial community structure in a poplar plantation.【Method】 The field experiment was designed at Dongtai Forestry Farm in Jiangsu Province, a coastal area of eastern China in June 2015, and we used Biolog ECO method and conducted nitrogen addition at four levels: N0(0 kg/(hm²·a)), N1(50 kg/(hm²·a)), N2(100 kg/(hm²·a)), and N3(150 kg/(hm²·a)). 【Result】The soil microbial C-source metabolic capacity was improved under N2 treatment, but was inhibited under higher levels of nitrogen deposition. Utilization of phenols and amines were the highest in N3 and N1, respectively. Average well color development(AWCD)and the Shannon diversity index were both significantly and positively correlated with nitrate nitrogen content(P<0.05), indicating that the C-source metabolism and community structure were influenced significantly by nitrate nitrogen content. The PC1 and PC2 in a principal component analysis(PCA)accounted for 50.04% and 25.02%, respectively, of the variation in microbial community metabolic diversity caused by nitrogen deposition. The PC1 was correlated with carbohydrates(-0.869), phenols(-0.780), amino acids(0.702)and carboxylic acids(0.821). The PC2 was correlated with polymers(-0.688)and amines(0.802).【Conclusion】After two years of nitrogen addition during May-October each year, the nitrogen amendment significantly changed the types of carbon utilized by the microbial community. There were significantly positive correlations between the contents of soil nitrate nitrogen and bacterial carbon metabolism levels as well as the diversity indices. The results of PCA indicated that the dominant carbon sources were carbohydrates and carboxylic acid.