Using melon seedlings grafted on three kinds of rootstocks and non-grafted seedlings as test materials inthis experiment, the effect of low temperature and poor light on the protection activity and photosynthesis of melonseedlings were studied and their tolerance to low temperature and poor light identified. The results showed that astreatment time prolonged, the activities of superoxide dismutase（SOD）, peroxidase（POD） and catalase（CAT） obvi-ously increased and then decreased rapidly, malondialdehyde（MDA） contents increased continuously. Low tempera-ture and poor light stress on protective enzyme system induced enzyme system to increase their activity, but activityof active oxygen scavenging enzymes decreased after long-term stress, which leading to cell membrane damage. Pho-tosynthetic rate（Pn）, Stomatal conductance（Gs）, Intercellular CO₂ concentration（Ci） and transpiration rate（Tr） ofmelon grafted seedlings were higher than own-rooted seedlings, and large differences existed among different graft-ed seedlings. Resistance to low temperature and poor light of Xuezhongjia was the strongest, next was Japanesepumpkin, Zhahamu was the weakest, and melon seedlings grafted on three kinds of different rootstocks were higherthan own-rooted seedlings.