Abstract: Taking ‘Jinyou 101’ cucumber as test material, the effects of high temperature and high humidity on the light response curve, catalase activity（CAT）,superoxide dismutase activity（SOD）,peroxidase activity（POD） and malonaldehyde（MDA） content of cucumber seedlings were studied in the Meteorological Laboratory of Nanjing University of Information Technology from May to September 2020,in order to provide reference for monitoring and early warning of high temperature and high humidity meteorological disasters and environmental optimization and control.The results showed that under the same humidity, the net photosynthetic rate（Pn） of leaves decreased with the increasing of high temperature stress.The activities of the three enzymes increased with the increasing of the degree of high temperature stress.MDA content increased with the increase of high temperature stress.At the same temperature, Pn decreased with the increase of humidity stress, but the degree of change was smaller than that of temperature stress.The activities of the three enzymes first increased and then decreased with the increasing of humidity stress.MDA content was the highest under 70% humidity treatment.Under the combined treatment of high temperature and high humidity, Pn decreased with the increase of stress temperature and humidity.The changes of the three enzymes activities were consistent with those under high temperature stress.The content of MDA increased with the damage of high temperature to cucumber seedlings, and its stress resistance also increased.Conclusion: the effect of high temperature stress on the net photosynthetic rate of plants was greater than that of humidity stress.The net photosynthetic rate decreased under 70% humidity treatment, and 70% humidity treatment could alleviate the harm of high temperature.