Abstract: The effects of exogenous nitric oxide on growth and oxidative damage in pumpkin seedlings under low temperature stress were studied. Seedlings of two pumpkin cultivars, ‘Yinhui 2’ and ’Qingli’, were sprayed with the nitric oxide donor, sodium nitroprusside (SNP: 100 μmol/L) and their growth, chloroplast pigment content, organic osmoregulation substances content, and active oxygen metabolism under chilling stress were analyzed. Chilling stress significantly inhibited the growth of pumpkin seedlings as a result of increased active oxygen accumulation and lipid peroxidation, decreased photosynthetic pigment content, and reduced osmotic adjustment ability. Under normal growth conditions, the SNP treatment significantly increased the activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR), and also significantly increased shoot dry weight, root dry weight, and the H₂O₂, free amino acid, glutathione, and carotene contents. Under chilling conditions (8 ℃ days/5 ℃ nights), seedlings sprayed with 100 μmol/L SNP showed significantly increased plant growth and dry matter accumulation and significantly increased SOD, POD, APX and GR activities in leaves, and reduced accumulation of H₂O₂ and malondialdehyde (MDA). Exogenous SNP application increased the glutathione, chlorophyll, carotenoid, ascorbate, soluble protein, and total amino acid contents. Under chilling stress, exogenous SNP application reduced the accumulation of H₂O₂ and MDA, and protected membrane stability by increasing antioxidant enzyme activities and the contents of organic osmoregulation and antioxidant substances. These physiological changes protected the stability of cell membrane structure, and maintained carbon and nitrogen metabolism in the seedlings under chilling conditions, thereby increasing the cold resistance of pumpkin. Under these conditions, Yinhui 2 was more responsive than Qingli to exogenous SNP.