An in situ experiment was conducted to study the effects of simulated nitrogen deposition on the litter decomposition in Neosinocalamus affinis stands in rainy area of West China. Four treatments were installed, i.e., null N (CK, 0 kg x hm(-2) x a(-1)), low N (LN, 50 kg x hm(-2) x a(-1)), medium N (MN, 150 kg x hm(-2) x a(-1)), and high N (HN, 300 kg x hm(-2) x a(-1)). Among the litters, leaf had the highest decomposition rate, followed by sheath, and twig, with a remaining rate after decomposing for 15 months being 26.38%, 46.18%, and 54.54%, respectively (P < 0.01). Leaf litter decomposed faster during the first 2 months and the 7th-10th month, while the decomposition of sheath and twig was faster from the 5th to the 8th month. It took 2.573 years to decompose 95% of leaf litter mass, 1.686 years and 3.319 years shorter than that of sheath and twig, respectively. After 15 months decomposition of leaf litter, no significant differences were observed among different treatments. To decompose 95% of sheath litter needed 2.679-4.259 years, being the longest in CK and the shortest in treatment MN. After decomposing for 15 months, the decomposition rate of twig litter was in the order MN > HN > LN > CK, and significant difference existed between treatments MN and LN. Nitrogen deposition had obvious promotion effect on the litter decomposition in the N. affinis stands, but this effect decreased with increasing deposited N concentration and time extension.