Effects of elevated nitrogen deposition on soil microbial biomass carbon (C) and extractable dissolved organic carbon (DOC) in three forest types of southern China were studied in November 2004 and June 2006. Plots were established in pine forest (PF), pine and broad-leaf mixed forest (MF) and monsoon evergreen broad-leaf forest (MEBF) in Dinghushan Biosphere Reserve. Nitrogen treatments included Control(no N addition), Low-N(50kg N hm^-2a^-1), Medium-N(100kg N hm^-2a^-1) and High-N(150kg N hm^-2a^-1). Microbial biomass C and extractable DOC were determined using the chloroform fumigation-extraction method. Results indicated that microbial biomass C and extractable DOC were higher in June 2006 than in November 2004, and were higher in MEBF than in PF or MF. Responses of soil microbial biomass C and extractable DOC to N deposition varied depending on forest type and the N treatment level. In PF or MF forests, no significant effects of N addition were found on soil microbial biomass C and extractable DOC. In MEBF forest, however, soil microbial biomass C generally decreased with increasing N addition, and high N addition significantly reduced soil microbial biomass C. The response of soil extractable DOC to N addition in MEBF showed the opposite trends to soil microbial biomass C. These results suggest that N deposition may increase the accumulation of soil organic carbon in MEBF in the study region.