Elevational patterns of non-volant small mammal species richness and its causes were studied along a central Himalayan gradient, in China, for the first time. We conducted field surveys at each of twelve elevational bands of 300 m for two times throughout the whole wet season between 1800-5400 m asl. In all, 755 individual small mammals of 22 species were documented in 21,600 trap nights. The species richness pattern for non-volant small mammals along the elevational gradients was hump-shaped, with highest richness at 2800-3100 m asl. Environmental factors played more important roles in shaping elevational species richness patterns than spatial factors. Our study also demonstrates that no single key factor can explain all species richness patterns, and a multiple or interacting causal framework for elevational patterns of species richness along the elevational gradient seem to be supported.