Abstract: Effect indexes of high temperature forcing on casaba and its physiological reasons are revealed through contrast experiments during its reproduction growth period．Results show that high temperature being higher to equal as 40℃ does harm tO casaba during its reproduction growth period，and its harmed degree has a direct ratio to high temperature intensity and duration．Damaged temperature of pollen avidity is much lower than that of lamina；that of lamina cell theca is higher or equal to 50℃ ，that of chlorophyll is higher or equal to 41℃ ，temperature that has the effect on pollen avidity is higher or equal to 31℃ ．Temperature higher or equal to 52℃ does obvious harm to nutrition and procreation organs of casaba．Experiment show that the leaves conductance rate increases ，chlorophyll content and farina vigor decline with the prolongation of the high temperature days．Treated with high temperature for 3 days，conductance rate of leaves at interspace and undersurface is 70％ more than antitheses．1eave chlorophyll content is 20％ less than antitheses and the percentage of high farinavigor is only 20％．1ess 1／2 than antitheses by I-KI coloration．