Plant carbon,nitrogen,and phosphorus balance has been a hotspot and focus of biogeochemical cycle and global change ecology research. However, previous studies mainly focused on the nutrient of leaves, relatively few study were conducted on the root. In present study, we investigated root C: N: P of S. purpurea and its relationships with environmental factors at 34 sites along a 1 300 km transect (Anduo - Naqu - Bange - Shenzha - Nima -Gaize - Geji - Gaer) across the alpine grassland of Northern Tibet. The result showed that root C, N and P concentrations ranged from 357. 17 to 458. 99 mg/g, 6.49 to16. 42 mg/g, 0. 22 to 0.77 mg/g, respectively. The root N concentration of S. purpurea had a similar value with the N concentration of global roots,whereas the P concentration was much lower than those of global root. Latitude,longitude and precipitation significantly influcenced root C :N: P,while altitude and temperature had no effects on root C: N: P stoichiometry. Our research suggested that the strong relationship between root C: N: P stoichiometry and geographic, climate factors and soil nutrient concentrations reveal that,to some extent,stoichiometry characteristics of S. purpure are adaptive to local environmental factors. Exploring the influences of environmental factors on root C: N: P stoichiometry is helpful for us to reveal plant nutrients allocation and utilization strategies in extreme environments, offering insights into quantifying the responses of alpine ecosystem to future climate changes.