Abstract: In order to understand the physiological mechanism of cold tolerance on Rhododendron hybridum, taking the variety of ‘Fenhong’ as materials to study the relative electric conductivity, MDA content, soluble sugar content, proline content, soluble protein content, SOD activity, CAT activity, POD activity and other physiological indexes under low temperature stress condition. From the chart we can know that with the stress time prolonged, the proline content kept steady, relative electric conductivity and MDA content increased gradually, soluble sugar content, soluble protein content, SOD activity, CAT activity and POD activity kept rising. The lower the temperature was, the higher the relative electric conductivity, MDA content, soluble sugar content, proline content, soluble protein content, SOD activity, CAT activity and POD activity would be. When the temperature was below 3℃, ‘Fenhong’ suffered serious damage, the lower the temperature was, the more serious degree of damage, after four days low temperature stress under 0℃, the cold acclimation of ‘Fenhong’ was greatly improved.