Abstract: 【Objective】 To study the photosynthetic characteristics of jujube leaves of different varieties in response to extreme high temperature in the hope of laying a foundation for stress resistance, high yield and efficient cultivation of jujube trees. 【Methods】 The two varieties with obvious high temperature resistance and the changes of high temperature stress were measured by Li-6400 photosynthetic meter at the day temperature / night temperature of 42℃ / 30℃. 【Results】 High temperature made the stomata of Junzao leaves closed, reduced the gas exchange inside and outside the cells, thus less CO₂ going into the cells, and the water utilization efficiency was reduced, both of which could not meet the needs of photosynthesis, resulting in the reduction of leaf photosynthetic rate; The net photosynthetic rate (Pn) of jujube leaves did not change significantly during the continuous 7 d high temperature stress, the net photosynthetic rate and transpiration rate was significantly positively correlated (P<0.01), net photosynthetic rate and intercellular CO₂ concentration was of significant negative correlation (P<0.01), so that the stoma was not completely closed, and there was still gas exchange.The leaves transpirated through the pores, taking away part of the heat to reduce the leaf temperature, reducing the impact of high temperature on the photosynthesis of Fucuimi jujube leaves.During the continuous high temperature stress period, the photosynthesis weekly change of the leaves in different branches of the jujube was always higher than that of the Junzao, and the jujube had a stronger ability to adapt to the high temperature stress.The shoots of jujube are more photosynthesis than the leaves of biennial branches, with the strongest ability to adapt to high temperature stress. 【Conclusion】 High temperature makes the water utilization efficiency and stomatal conductivity of jujube leaves decrease, which leads to the decrease of photosynthetic rate.The different branches of the leaves have stronger high temperature resistance, among which, the new leaves of Fucuimi have the strongest high temperature resistance, and can best adapt to the high temperature environment.