Abstract: Eight Hydrangea macrophylla cultivars were selected as experimental materials.The changes of cell injury rate of functional leaves of Hydrangea macrophylla at 35,40,45,50,55,60,65 ℃ and 70 ℃ were measured by conductivity method.The semi-lethal high temperature was obtained by logistic equation fitting, and the adaptability of different Hydrangea macrophylla cultivars to high temperature environment was compared.In order to evaluate the heat resistance of Hydrangea macrophylla cultivars, and provide a reference for the application of Hydrangea macrophylla cultivars in urban and rural landscaping in Southern China.The results showed that after high temperature treatment, the cell injury rate and treatment temperature showed a typical ‘S’ curve model, and the significance test was in accordance with the logistic equation.The semi-lethal high temperature range of the eight Hydrangea macrophylla cultivars ranged from 54.81 ℃ to 60.07 ℃,and the order of heat resistance from strong to weak was ‘Princess Charlotte’（60.07 ℃）＞‘Stockings’（57.67 ℃）＞‘Endless Summer’（57.07 ℃）＞‘Taube’（56.95 ℃）＞‘Stiletto’（56.94 ℃）＞‘Mona Lisa’（56.64 ℃）＞‘Endless Summer Bride’（56.35 ℃）＞‘Kasumi’（54.81 ℃）.According to the semi-lethal high temperature,the above cultivars could be divided into three groups,the first group ‘Princess Charlotte’was a more heat-resistant cultivar,with an average semi-lethal high temperature of 60.07 ℃.This cultivar was a potential excellent cultivar applied in hightemperature areas;the second group included‘Tricolor’‘Stockings’ ‘Endless Summer’‘Taube’‘Stiletto’‘Mona Lisa’were moderately heat-resistant cultivars,with an average semi-lethal high temperature of56.94℃;the third group included only ‘Kasumi’that was not heat-resistant,with an average semi-lethal high temperature of 54.81℃.It was more suitable for planting in lower temperature areas.