To understand the in-depth impacts of nitrogen deposition on the processes of litter decomposition, a field litterbag experiment was conducted in a natural evergreen broad-leaved forest in the rainy area, West China, from March 2016 to 2017. Microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) during litter decomposition were investigated under four levels of simulated nitrogen deposition treatments, including control (CK, 0 g N m^-2 a^-1), low nitrogen (LN, 5 g N m^-2 a^-1), medium nitrogen (MN, 15 g N m^-2 a^-1) and high nitrogen (HN, 30 g N m^-2 a^-1) deposition. The results showed that LN and MN treatments significantly increased MBC and MBN during litter decomposition, but a higher increase was observed under LN than under MN treatment. LN and MN treatments did not significantly affect MBP during litter decomposition. However, HN treatment significantly reduced MBC, MBN, and MBP. The microbial biomass C/N decreased gradually with an increase of N deposition levels, although the microbial biomass C/P initially increased and then decreased. The results indicated that nitrogen deposition could play an important role in litter decomposition processes by regulating microbial biomass.