Abstract: Twenty melon varieties treated under low temperature and weak light at their seedling stage were used to assess the low temperature and weak light tolerance and to select the indicators by the correlation analysis， principal component analysis and cluster analysis. A total of 12 indicators （plant height， stem diameter， shoot fresh weight， root fresh weight， shoot dry weight， root dry weight， leaf number， root length， root surface area， root volume， roottip number and root projected area） of melon at seedling stage were measured after low temperature and weak light stress. Correlation analysis and principal component analysis showed that there were positive correlation between 12 morphological indexes of melon， but the correlation between root length and root dry weight is not significant. Use the cluster analysis， 7 varieties with resistance to low temperature and weak light stress and 1 sensitive variety were screened out. A tolerance equation of melon seedlings was established by stepwise regression analysis， in which relative root fresh weight， relative root length， relative leaf number， relative root surface area and relative root projected area could be used as identification indicators of melon resistance to low temperature and weak light.

Key words: melon, low temperature and weak light, cluster analysis, principal component analysis