Abstract: The variations of SOD activity, POD activity, permeability in winter with six hybrid clones of Populus tomentosa were investigated. The results show that the SOD activity variation of the clones can be divided into two types and the variation patterns of other indexes were similar. The difference in the indexes value among the clones was significantly different, in December the permeabilities in all clones examined were lowest and the ability of cold resistance was highest. The results of comprehensive evaluation according to the indexes also show significant differences among the clones. There were significant correlation between the indexes and the result of comprehensive comparison.