Abstract: In order to study the effect of melatonin on the storage quality and energy metabolism of postharvest green pepper (Capsicum frutescens L.). The green pepper was used as the experiment material in this experiment with different concentrations (100, 200 and 300 μmol/L) at low temperature (9 ℃). To investigate the effects of melatonin treatment on the storage quality and energy metabolism of green pepper fruits. The results showed that melatonin treatment could effectively reduce decay rate and slow down the decline of fruit hardness of green pepper. In particular, the treatment effect of 200 μmol/L melatonin was the best. In addition, melatonin could delay the decline of capsaicin and chlorophyll content, maintained a lower MDA content, inhibited the degradation of ATP, ADP and AXP, promoted the accumulation of AMP content, and maintained a higher energy charge level in green pepper. Melatonin could also maintain high SDH, CCO, H⁺-ATPase and Ca²⁺-ATPase activity in green pepper. Correlation analysis showed that the activities of ATP, ADP, AXP, energy charge, H⁺-ATPase and Ca²⁺-ATPase in green pepper were significantly negatively correlated with the decay rate (P<0.05), and were significantly positively correlated with the contents of capsaicin and chlorophyll (P<0.05). Moreover, the activities of ATP, ADP, AMP, AXP, energy charge, H⁺-ATPase and Ca²⁺-ATPase in green pepper were significantly positively correlated with each other (P<0.05), indicating that melatonin treatment could explain that the quality of postharvest green pepper was closely related to energy level during storage. The results of this study can provide technical reference for the application of melatonin in controlling the storage quality of postharvest green pepper.