Leaf litter decomposition responds differently to elevated nitrogen (N) deposition across various litter species. However, the potential of the microbial decomposer community to explain this apparent stochasticity remains largely untested. We conducted a litter decomposition experiment using litter bags under an N gradient to address how litter quality and litter-dwelling microbial decomposers jointly mediate the effects of exogenous N on the process of litter decomposition. The litter quality was differentiated by C/N ratio and lignin content, and the microbial community was assessed using a fungal internal transcribed spacer (ITS) and bacterial 16S rRNA gene (16S) amplicon sequencing throughout the decomposition process. We found that medium (70 kg ha-1 yr-1) and high (105 kg ha-1 yr-1) levels of N addition decreased the decomposition rate (k) of lower quality litter (Castanopsis chinensis, CC), whereas none of the N treatments reduced the decomposition rate of higher quality litter (Schima superba, SS). Unexpectedly, N addition generally increased the microbial alpha-diversity in the CC litter but decreased the microbial alpha-diversity in the SS litter. The reduced decomposition rates of the CC litter in medium and high N treatments correlated with a decrease in the relative abundance of ligninolytic fungi (Mycenaceae of Agaricales, Hydnodontaceae of Trechisporales, Corticiales). In the SS litter, these fungal groups did not decline with N treatments, and the relative abundance of the ligninolytic fungi, Agaricales (Marasmiaceae), increased with high N addition. The reduced relative abundance of the ligninolytic fungi contributed to a decreased litter decomposition rate of lower-quality litter via high N addition