The seedlings of melon‘Jinong 12’under low temperature and poor light were foliar-sprayed with different concentration of SA, then the leaf physiological characteristics and antioxidant enzyme activities were measured.The results showed that foliar spraying of 1.0 mmol/L and 1.5 mmol/L of SA before the stress, the leaf activities of superoxide dismutase（SOD） activity after 4 days, peroxidase（POD） activity after 3 days and catalase（CAT） activity after 2 days significantly increased, the leaf photosynthetic rate（Pn）, stomatal conductance（Gs）, transpiration rate（Tr）increased compared with CK（water treatment）, while the heintercellular CO₂ concentration（Ci） and malondialdehyde（MDA） content decreased. However, in treatment of foliar spray of 2.0 mmol/L of SA before the stress, Ci and MDA increased, while other indexes decreased compared with CK. All of these results suggested that SA could regulate the leaf photosynthetic functions of melon seedlings, and enhance the seedlings resistance against low temperature and poor light. The optimum concentration of SA for the foliar spraying was 1.0 mmol/L and 1.5 mmol/L.