Abstract: The arid regions of China include Mongolian- Xinjiang warm-temperate arid region and Qinghai-Xizang frigid arid region, located in western China, host 120 species of small mammals including Largomorpha and Rodentia. We collected all of the available distributional data for these species in these regions. Based on GIS models of species range which were predicted by a wildlife-habitat model, we researched the distribution patterns of rodent diversity there. A total of 766 equal-area quadrangle grids that each had an area of 6,470 square kilometers were used as geographic units to collect distributional data of the species, supported by MapInfo Professional Version 4.0. Based on these grid data we obtained the number of genera and families, and calculated the small mammal species diversity of genera and families by Shannon-Winner index and G-F index. In order to explain the species differentiation tendency of small mammals, we introduced number ratios of species to genera and of genera to families as differentiation indices. The results indicate that more genera occurred in mountains around the Junggar Basin, Qilian Mountains, Helan Mountains and the west slopes of Da Hinggan Mountains, where species richness was higher, as might be explained by an edge effect. In contrast, richness was least on the Ordos Plateau and Zhangbei Plateau. There were more families on the south slopes of the Altay Mountains, Tianshan Mountains of Ili and East Qilian Mountains, but fewer on the Ordos Plateau and Zhangbei Plateau. High species diversity often occurred in ecotones such as those among or between frigid desert and warm-temperate desert, desert and mountains, plateaus and basins, desert and steppes, and mountains and steppes. In the Qinghai-Xizang Plateau, number ratios of genera to families were much lower than in the Mongolian-Xinjiang region. In contrast,, there were higher ratios of species to genera in the former region. The G-F index was higher in Qinghai-Xizang Plateau, where a great species differentiation was implied. Since small mammals can be used as indicators of biodiversity, the distributional patterns of their species diversity could be helpful for assessment of biodiversity in arid regions of West China.