Abstract: Taking 20-year-old ‘Red Fuji’ apple as test material, the effects of different concentrations of exogenous calcium on MDA content, SOD activity, POD activity and CAT activity in apple flower organs were studied by using artificial climate chamber to simulate low temperature freezing injury.The comprehensive evaluation of cold resistance was conducted by using the membership function method.The results showed that under low temperature stress, the content of MDA in different concentrations of exogenous calcium decreased by 10.7%-53.6% compared with the control, and the differences were extremely significant.All treatments except 28 mmol·L^-1 CaCO₃ increased SOD activity, and all treatments except 14 mmol·L^-1 Ca（NO₃）₂ showed extremely significant difference compared with the control.Different concentrations of exogenous calcium increased the POD activity, except 14 mmol·L^-1 and 28 mmol·L^-1 Ca（NO₃）₂ treatments were significantly different from the control.Compared with the control group, CAT activity increased by 8.7%-22.7% with different concentrations of exogenous calcium, and showed extremely significant differences with the control group.In conclusion, four physiological indexes, including malondialdehyde content, catalase activity, peroxidase activity and superoxide dismutase activity, can be used to identify the cold resistance of apple.The membership function value analysis showed that the apple flower organs treated with 21 mmol·L^-1 CaCl₂ had the best cold-resistance effect.