In order to quickly and effectively screen the heat tolerant leaf lettuce（Lactuca sativa L.） cultivars with superior quality，and realize its heat tolerant cultivation in summer，we selected 36 leaf lettuce cultivars from home and abroad，and carried out comparative cultivation experiment under
high temperature of artificial simulation，then determined and analyzed the heat injury index，root system activity，leaf relative conductivity and content of oxygen free radicals in leaf blades．Based on the above screened indexes，we chose‘Kasitenaiyoushengcai’，‘Kuxiye’，‘Xibanya’，‘Shuangzijieqiushengcai’，and‘Meiguojieqiushengcai’as leaf letterce cultivars with relatively higher tolerance to high temperature．