With low-light sensitive tomato variety ‘Jiersi’ as the tested material,we investigated the effects of exogenous 24-epibrassinolide（EBR） on the growth,gas exchange parameters,chlorophyll fluorescence parameters,chlorophyll content,anti-oxidative enzyme activities and MDA content of tomato seedlings under low light stress by hydroponic culture.The research showed that there were significant effects on the growth and physiological function under low light.However,in the treatment of foliar spraying EBR for 15 days under low light,the stem diameter,shoot fresh weight,dry weight and healthy index of tomato seedlings were significantly increased by 15.8%,29.3%,79.0% and 114.5%,respectively；Net photosynthetic rate（P_n）,stomatal conductance（G_s） and transpiration rate（T_r） were significantly enhanced by 34.1%,46.3% and 35.9%,respectively；Chlorophyll fluorescence parameters F_v/F_m,Ф_PSⅡ and ETR were raised by 21.0%,15.4% and 16.7%,respectively；SOD,POD,CAT and APX activities were increased by 16.7%,31.8%,32.7% and 51.2%,respectively.The plant height,leaf area,intercellular CO₂ concentration（C_i）,chlorophyll content and MDA content were decreased by 9.8%,13.9%,0.9%,13.2% and 19.5%,respectively.Hence,it was indicated that appropriate amount of exogenous EBR could mitigate lipid peroxidation injury by strengthening the protective enzymatic system activity,alleviate non-stomatal limitation which inhibited photosynthetic function under low light,and maintain the photosynthetic activity,promote growth.