Abstract: 【Objective】 To study the effect of snow cover on cold resistance and winter surviving rate of different fall dormancy alfalfa. 【Methods】 The contents of WSC,SP,Pro,MDA,SOD and POD in alfalfa roots and their overwintering rate were measured from autumn to next spring without snow and natural snowfall and winter surviving rate. 【Results】 Under no-snow cover,the lowest average temperature of alfalfa root canopy was -20.74 ℃,and 20 cm of soil fluctuated between -5 and -10℃;under snow cover,the lowest temperature of alfalfa canopy was -7.89℃,and the temperature of 20 cm of soil kept above -3℃ during most of the measurement period,which indicated that snow cover could improve the temperature of alfalfa canopy and soil. Under no snow cover, the winter surviving rate of semi-fall dormancy and non- fall dormancy alfalfa was significantly lower than that of fall dormancy alfalfa(P<0.05). the winter survival rate of semi-fall dormancy and non-fall dormancy (grade 7) alfalfa increased more than 85%,which indicated that the winter survival rate of high fall dormancy alfalfa could be significantly increased by covering snow(P<0.05). The content of root protective substance increased with the decrease of air temperature, and maintained at a high level in winter. The contents of WSC,SP,Pro,MDA,SOD and POD in the roots of fall dormancy alfalfa were higher than those of no snow covering kinds,and the content of MDA was lower than that of no snow covering kinds. Snow could significantly improve the cold resistance of fall dormant alfalfa(P<0.05). 【Conclusion】 It can be concluded that covering snow can significantly improve the cold resistance and winter surviving rate of high fall dormancy alfalfa, and the suitable planting alfalfa in Shihezi area is Zhaodong and Zhongmu No.2 (grade 1 and 3).