Abstract: The autumnal changes in contents of carbohydrate, soluble protein and the enzyme activities of catalase (CAT) and superoxide dismutase (SOD) in the root of Clinelymus nutans (griseb) Nevski were studied in the cold mountain areas, The results showed that both the contents of carbohydrate and soluble protein and the enzyme activity of the CAT and SOD increased with the temperature decrease in Autumn and early Winter; and these four attributes were higher in the forage root collected in the burned grassland than that in the non-burned grassland. Since the high contents of carbohydrate and protein in the forage root at the end of Autumn could provide energy for forage to resistant cold in Winter and provide nutrients for forage ger mination in the following year, the forage in the burned grassland grew better than that in the non-burned grassland. The high enzyme activity of the CAT and SOD in the Autumn was also related to a high resistance to low temperature.