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Wild native Elymus (Elymus dahuricus) is one of the most important and valuable forage grass on Qinghai-Tibetan Plateau (QTP) pasture of China. It mainly distributes above sea-level of 1700 to 3000 m on the QTP. The objective of this study was to investigate how the nutritive composition of Elymus responsed to the changes of altitude in local environments. Two test sites located at Minghe and Huangzhong counties, in which four sampling plots were arranged with sea levels of 1714, 1872, 2097 and 2185 m in Minhe County, while other four in Huangzhong County were with sea-level of 2560, 2613, 2668 and 2775 m. The whole plants of Elymus during anthesis stage were collected from all the plots for determining the indexes of crude protein (CP), crude fat (CF), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude ash (ASH), calcium (Ca) and phosphorus (P). The results showed that the content of CP, crude ash and Ca changed irregularly corresponding to the altitude in the two counties, but significant higher with CP (1.09％), Ash (0.33％) and Ca (0.34％) in the low altitude areas (1714 - 2185 m) than those in the high altitude areas. NDF and ADF in the low altitude areas were significantly lower by 5.35％ and 2.61％ compared with those in the high altitude areas. There was no significant difference of CF as well as P in plant from different altitudes. Comprehensive evaluation revealed that superior nutritional composition of Elymus dahuricus presented at the sampling plots of altitude of 1714 m in Minhe County.