We analyzed the spatial niche breadth and spatial niche overlap of 18 species of small mammals in five habitats at Haidong region in Qinghai Province. Niche breadth indices of 18 species varied from 0 to 1. Microtus limnophilus had the highest index of the niche breadth (0.940) while Caryomys eva , Apodemus agrarius , Rattus norvegicus, R.tanezumi, Niviventer confucianus , Tamias sibiricus , Pteromys volans , Sicista concolor , Sorex caecutiens had the lowest index of the niche breadth, approximation to zero. Niche overlap indices also varied from 0 to 1. Those species that had completely spatial niche overlap indices would have very similarly biological characteristics and ecological adaptability. When the resources are abundant, small mammals use the resources altogether, otherwise it may lead to competition. Niche species that do not overlap showed obviously differences in using the natural resource and no competition due to significant niche differentiation.