Abstract:A sample plot of a Cunninghamia lanceolata plantation (38 a) in Fujian Sanming Forest Ecosystem National Observation and Research Station in subtropical China was selected to investigate the effects of nitrogen (N) addition on soil organic carbon(SOC) mineralization. Three N addition levels, N0 (0 mg/kg), N10 (100 mg/kg) and N25 (250 mg/kg) were set in a culture experiment which was carried out for 117 days. The results show that: 1) SOC mineralization rate reaches the maximum on the first day. At the early stage of culture (0-57 days), the mean organic carbon mineralization rate of N0, N10 and N25 treatments decreased significantly by 44%, 45% and 47%. During the culture period, the average SOC mineralization rate is 9.97 mg/(kg·d) under N0, 9.27 mg/(kg·d) under N10 and 8.89 mg/(kg·d) under N25. 2) The cumulative amount of SOC mineralization is increased significantly with the extension of culture time, and decreased significantly with the increased of N addition. Compared with N0, the average value of SOC mineralization accumulation is decreased by 3.4% under N10 and 7.4% under N25, respectively, after incubation for 117 days. 3) The response of microbial biomass to N addition is not significant, but the ratio of fungi to bacteria is increased with N addition. In general, N addition inhibits SOC mineralization mainly by changing soil C and N contents. Therefore, the change of soil C and N nutrient contents after N addition is the main reason for the change of SOC mineralization rather than the change of microbial community structure.