Abstract:Research on the dynamic variation of cold resistance in forage′s root system has great importance for forage introduction and screening, especially in cold areas. Using Poa Aalpine, Elymus junceus, Agropyron inerme, Agropyron inerme（Secar） and Agropyron inerme（Goldar） as experimental materials, the dynamic variation of MDA、SOD、soluble sugar and protein in the of different grass species were investigated in different growth phases treatments of cold acclimation, freezing treatment, thawing and recovering growth under controlled temperature condition. The results indicated that for all the materials, the content of MDA increased a little in cold acclimation treatment and then maintained basically stable; The activity of SOD increased in cold acclimation treatment and decreased dramatically under freezing treatment, then after thawing, it increased again in recovering treatment and the increase was significant; The content of soluble sugar, protein and proline showed the same tendency of increasing in acclimation and freezing treatments, and decreasing in turning green treatments. Furthermore, unlike SOD activity, soluble sugar content and proline content, the variation of MDA content and soluble protein content are not significant under different treatments. At last, by using fuzzy mathematics method, the cold resistance ability of those gramineous grass species tested was evaluated as Poa Aalpine＞Elymus junceus＞Agropyron inerme（Secar）＞Agropyron inerme＞Agropyron inerme（Goldar）.