Abstract: Physiological and biochemical characteristics of the leaves of six Elymus species were determined under the natural dry farming conditions of the arid and semi-arid regions of Inner Mongolia, different species from same regions were compared as well as the same species from different regions. There were significant differences in the physiological and biochemical characteristics of different Elymus. The species of XJE1 and XJP5 maintained a good water status and had a high relative water content (RWC), whereas the RWC of GSD4 was the lowest. BJT3 and XJP5 had a high chlorophyll content, while that of GSD4 was low. The osmotic content of Pro of BJT3, XJP5 and GSS2 was significantly (P<0.05) higher than that of the other species. The MDA of BJT3 was nearly three times higher than that of XJE1. GSD4 had the most SOD antioxidative enzyme activity, followed by BJT3 and then GSS2. POD activity of XJP5 was high, followed by BJT3, while NMN6 was lower. Multivariate membership function analysis indicated that except for GSD4 and NMN6, there were some significant differences in adaptation to arid and semi-arid environmens of the Elymus species. The order of subordinate function values from strong to weak was XJP5＞BJT3＞XJE1＞GSD4＞NMN6＞GSS2. We also found that there were some homologies between different species from the same region. The same species in different regions appeared to be differentiated in their adaptability. These results indicate that the physiological and biochemical indexes were all adapted to different ecological environments.