Abstract: In order to investigate the regulation mechanism that exogenous putrescine (Put) treatments on reducing chilling injury of postharvest yellow melon fruits, ‘Xinmi No.3’ yellow melon fruits was used as material, and the effect that exogenous putrescine ( 0 and 2.0 mmol/L Put) treatments on the chilling injury were studied and reactive oxygen metabolism of yellow melon fruits under 5±0.5 ℃ temperature. The results showed that 2.0 mmol/L Put treatment could maintain higher level of superoxide dismutase (SOD) activity, furthermore, it could increase the activity of catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) 2.3, 1.6, 1.2 times, respectively compared with CK at 21 days (Severe chilling injury), and reached to 30.06, 2.46 and 39.14 U·g⁻¹ FW, respectively. It inhibited the accumulation of superoxide anion radical (O₂·⁻) and hydrogen peroxide (H₂O₂), the activity of lipoxygenase (LOX) and the content of malondialdehyde (MDA) at 28~49 days significantly, thus, it could alleviate the damage of reactive oxygen species to cell membrane, and relieved the symptoms of chilling injury of ‘Xinmi No.3’ yellow melon fruits, delay the occurrence time of chilling injury by 7 d, the chilling injury index was only 0.27 until at the end of storage period, it lower than the control significantly. Therefore, the exogenous putrescine (Put) treatment can alleviate chilling injury of yellow melon is closely related to balance reactive oxygen metabolism.