The damage mechanism of Shanghaiqing and its internal and external factors in the vacuum pre-cooling process were studied in this paper.Firstly,three groups of Shanghaiqing were used in the vacuum pre-cooling experiments under 600Pa,700 Pa and 800 Pa;In each pre-cooling process,three thermocouples marked No.0,No.1,No.2 were individually stick to its different parts(main vein,fine vein and margin) to measure their temperature changes with the time;then,the frostbitten parts of leaves in these three vacuum pre-cooling processes were peeled and sampled in the study of comparing the sizes of their mesophyll intercellular spaces.Results show that: in this vacuum pre-cooling cooling-damage experiment,under the different final pressures,the leaves surfaces temperature distributions were all uneven and reduced from the main vein to fine vein and to the leaf margin where temperature was to-2℃ to-5℃,which caused the damage of frostbite of leaf margins;the average equivalent radius of the frostbitten mesophyll intercellular spaces at different conditions were 23.5 μm,19.2 μm and 17.3 μm.The conclusion is: in the vacuum pre-cooling processes for Shanghaiqing,leaf margin is most likely to be frostbitten by the mechanical force in the extra-cellular ice;and degrees of frostbite enhanced with the decrease of final pressures;for Shanhaiqing,the final pressure should set up more than 800Pa.