Abstract: The micro-scale environmental heterogeneity caused by topographical diversity is an environmental foundation underlying the formation and evolution of biogeographic pattern. Based on the field survey in July-August 2009, and with the help of GIS and S-PLUS software, a quantitative analysis with generalized additive model (GAM) was made on the relationships between the Oedaleus asiaticus abundance and topographical factors such as altitude, aspect, slope, and profile curvature in the natural grassland on northern slope of Qilian Mountains, the upper reaches of Heihe River. The model for O. asiaticus performed well, and could actually reflect the spatial distribution of O. asiaticus abundance. Different topographical factors had different effects on the spatial distribution of O. asiaticus abundance, among which, elevation and profile curvature showed dominant effects. With the increase of elevation, the O. asiaticus abundance showed a more or less reverse “V” trend. The abundance had a positive correlation with increasing altitude at altitude 2380-2560 m, but a negative correlation with the increasing altitude at altitude >2560 m. The O. asiaticus was mainly distributed in the regions with a profile curvature <0. There existed a positive correlation between the abundance and profile curvature when the profile curvature was <-1.6, and a negative correlation when the profile curvature was >-1.6. The relationships between the abundance of O. asiaticus and topographical factors as well as the spatial distribution pattern of O. asiaticus abundance indicated that the redistribution of water and heat conditions due to topographical factors caused the heterogeneity of the spatial distribution pattern of O. asiaticus.