Forest litter is an important part of forest ecosystem and its chemical property is called substrate quality, which is defined as the relative decomposability of litter and depends on the easy decomposition components of the organization. A number of studies have found that the substrate quality of litter is the main factor affecting the litter decomposition process, which is the key process of biological chemical cycle of forest ecological system. In order to investigate the effects of N deposition on the substrate quality of bamboo forest litter, a simulated N deposition experiment was conducted in a P. amarus plantation in Rainy Area of West China, from November 2007 to December 2010. Four treatments was installed, i.e., control (0 g N·m^-2·a^-1), low nitrogen (5 g N·m^-2·a^-1), medium nitrogen (15 g N·m^-2·a^-1) and high nitrogen (30 g N·m^-2·a^-1). From January to December in 2010, litter samples were collected each half month and the basic properties of litter quality (concentration of C, N, P, lignin and cellulose) were measured. The results indicate that simulated N deposition significantly increased the concentration of N and P in leaf litter and medium nitrogen treatment increased the N content of twig litter, meanwhile medium and high nitrogen treatments increased the P content of twig litter; The effects of simulated N deposition on concentration of C, lignin and cellulose were not significant. The C/N ratio of leaf litter and twig litter were decreased significantly. Results suggest that the litter decomposition rate in early stage of decomposition may be stimulated by simulated N deposition because of increasing N (decreased C/N ratio) and P in fresh fallen litter.