Abstract: Habitat selection of red deer (Cervus elaphus alxaicus) was studied from November to December,2003 in Helan Mountain which geographically locates in 38°21′-39°22′N,105°44′-106°42′E.Fourteen ecological factors of 87 sites used by red deer and 50 random plots were measured by locating from fresh sign or dung during 25 transects surveys crossing the whole study area.These factors included vegetation types,dominant tree,slope direction,slope location,food abundance,tree density,shrub density,slope degree,altitude,snow depth,distance to water resource,distance to human disturbance,distance to bare rock,and hiding cover.Red deer preferred montane grassland and montane conifer forest,and avoided subalpine shrubland and meadow;selected for mixture habitats,but rejection of habitats dominated by Juniperus rigida,Pinus tabulaeformis and no tree;utilized the paces with slopes exposed to the sun for lower slopes,and avoided shady slopes,upper and middle slopes.Comparing usage sites and random plots,usage sites were characterized by higher shrub density,higher food abundance,lower slope gradient,shallower snow cover and approach to water resource.Most sites were located farther away from bare rock and human disturbance.Results of principal component analysis showed that the 6 principal components explained 84.89% of the total variance.The first principal component was positively related to vegetation type,tree density,shrub density,slope direction,slope degree,distance to water resource,snow depth,and altitude.