Abstract: Abstract:The objective of this experiment was to analyze watermelon germplasm for resistance to low temperature and provide theoretical basis for breeding. 21 watermelon materials were tested by chilling index, electric conductivity, soluble protein, SOD, POD, and MDA in man-made simulate climate and all the results were clustered. Differences were found in chilling index among watermelon varieties. Wild watermelon chilling enduring level was higher than that of others while ZXG01315 was the lowest. There are significant differences in the electric conductivity. Wild watermelon was the lowest while super-sweet female parent was higher than that of others. The change of chlorophyll a/b in the lower temperature stress was divided into three types which were lower, rise and smooth. The more chilling enduring higher; the more soluble protein content and malondialdehyde increased greater. The more chilling enduring higher, the superoxide dismutase activity and peroxidase activity increased along with the temperature cut down. The cluster analysis divided the 21 varieties to 3 parts: the first part included only wild watermelon; the second and the third parts both included 10 watermelon materials. Watermelon parts have a close relationship with watermelon chilling enduring. The first and the third parts can be used as breeding materials