Litter decomposition is a fundamental ecosystem process, and climate and litter chemistry strongly control rates of litter decay. In this work, three forests along an elevation gradient on the eastern slope of Sergyemla Mountain were selected to compare litter decomposition and chemical fraction loss rates, and further to evaluate the effects of environmental factors and litter chemistry on the litter decomposition process. The leaf litter decomposition coefficient of the mixed conifer and broadleaf forest (MCBF, 3,169 m a.s.l.), sclerophyllous evergreen broadleaf forest (SEBF, 3,453 m a.s.l.), and subalpine dark coniferous forest (SDCF, 3,957 m a.s.l.) sites were 0.04, 0.03, and 0.02 month^-1, respectively. The litter mass loss at the MCBF site significantly correlated with litter quality, but that of the SEBF and the SDCF sites did not. In addition, there was a significant positive relationship between the litter mass loss and temperature along the elevation gradients. This study demonstrates that the litter decomposition rate decreases with increasing altitude along the elevation gradient. Climate is the key factor influencing litter decay across environmental gradients, but litter quality also affects decomposition rates in low-elevation forests.