Plant carbon (C), nitrogen (N), phosphorus (P) contents and their ecological stoichiometric ratios can reflect their adaptive characteristics under environmental changes. However, it is still unclear on the adaptive mechanisms of C, N and P stoichiometric characteristics in different plant functional groups under the change of elevation gradients. Therefore, sixty sites were selected from an alpine meadow in the western Sichuan Province to explore the variation of plant C, N, P contents and their ecological stoichiometric ratios (mass ratio) in different functional groups (grass, sedge, legume and forbs) and the key driving factors along five altitude gradients (3300-3500 m, 3500-3700 m, 3700-3900 m, 3900-4100 m and 4100-4300 m). The results showed that: 1) The alpine plants exhibited certain stoichiometric homeostasis, different altitudes did not significantly (P ＞ 0.05) affect the C contents in different plant functional groups, N contents of sedge and legume, P contents of grass, sedge and legume, as well as C : P and N : P in different functional groups except C : P of sedge. 2) Grass and forbs could adapt the alpine environment by increasing their nitrogen content with the altitude increasing. The P contents of legumes were lower at 4100-4300 m than 3700-3900 m (P ＜ 0.05), probably due to the decline of mean annual precipitation in high altitude. 3) Generally, the C : N of the four plant functional groups showed decreasing trend with the increase of altitude, which indicated that the increase of elevations led to a decrease in plant N use efficiency. Additionally, the N : P ratio of each plant functional group was more than 16, suggesting that plant growth was limited by P. 4) Compared with the other functional groups, legume showed higher N contents and N : P, but lower C contents and C : N. 5) Based on the redundancy analysis (RDA) and structural equation model (SEM), the contents of C, N, P, and their ecological stoichiometric ratios in different plant functional groups were regulated by the mean annual temperature and precipitation, which were then jointly influenced by altitude and latitude. In conclusion, plants exhibited the ecological adaptation strategies of increasing, decreasing, or maintaining the stability of their own C, N, P contents and their ecological stoichiometric ratios along the altitude gradient. These differences varied with different plant functional groups. Therefore, when constructing biogeochemical models of plant C, N, P, it is necessary to consider the differences in plant ecological adaptation strategies along the altitude gradient.