Abstract: The heat tolerance of four species in the family of Crassulaceae was comparatively studied by measuring their half lethal temperature with the relative electricity conductivity method and calculating the data with Logistic equation.The results showed that the relationship between the temperature for leaf treatment of the four plant species and the relative electricity conductivity varied in the ‘S’ curve model,which was accorded with Logistic equation proven by significance test.Calculated with the formulas,the half lethal temperatures of the four plant species were Sedum lineare 6024℃;S.reflexum 5469℃;S.spurium‘Coccineum’ 5281℃and Sedum spectabile 6281℃.According to the half lethal temperature,the heat tolerance of the four species in family Crassulaceae was in the order of Sedum spectabile>S.lineare>S.reflexum>S.spurium ‘Coccineum’.