This paper gives an analysis of the fatty acid component contents in the cell membrane of populus hybrids. The results of the analysis show there exist distinct differences in the proportion of fatty acid component contents among populus clones. The ratio of the unsaturated to saturated fatty acid in the cell membranci which shows the unsaturated level of fatty acid, is corelated positively with the ability of the frost resistance. The unsaturated level depends on the inheritance of different clones. More remarkable differences of the unsaturated fatty acid levels are found in the cell membrane of hybrid progenies of P. simonii (Shanxi) male parent; especially in the combination of P. deltoides cv. ’LUX’ (ex. I-69/55) × P. simonii (Shanxi). The paper considers that the ratios of linoleic (C18:2) to linolenic (C18:2)acid can be used as an index of the frost resistance of populus clones.