Abstract: After the plants of three wheat varieties with different cold resistance were frozen for two days at –9 ℃ and then thawed at room temperature, the freezing injury and recovery expression of shoots and ultrastluctural changes of their leaf cells were compared. The results obtained are summarized as follows: The fine structure in leaf cells of hardy variety Nongke No. 1 did not produce visible ohanges, and the plants recovered to normal morphology immediately after thawing. The cell ultrastructure of mediate-hardy variety Zhengzhou No. 741 showed significant changes which were reversible. The chloroplasts became round by different degrees, parallel arrangement of the lamellae in chloroplast was altered, and the thylakoid produced some vesicles, but the chloroplast envelope was still intact. The tonoplast exhibited infolded and engulfed structure. Nuclear ehromatin was coagulated to form bigger mass. The fine structure in leaf cells of non-hardy variety Jinghong No. 8 was severely destroyed. The chloroplasts were disintegrated. A lot of vesicles were formed in cytoplasm and nuclei. Mitochondria cristae were also disrupted. These changes are irreversible and lead to death of plants.