Abstract: Objective: In order to improve the viability of cryopreserved splitthickness skin and get a higher survival rate. It is necessary of verify the changes of tissues and cells damaged during 0~-40 ℃ region so as to supply the experimental basis to alleviate freezing injury.Methods: The skin splits without cryoprotectant were utilized to observe the viability changes and optimal freezing rate according to the graded freezing theory and methods of McGann.Results: Compared by two methods （oxygen consumption and WST-1） during graded freezing of 0~-40 ℃ under two cooling rates. The tendency of viability changes of cryopreserved split thickness skin of thaw group and LN 2 group were observed. Conclusion: Viability of the cryopreserved split thickness skin comes to balance under two cooling rates at -20 ℃.