Abstract: To investigate the effects of melatonin on the browning and quality of postharvest sweet cherry fruits, ‘Samituo’sweet cherry was used as the material in this study. Sweet cherry was treated with distilled water and 100 μmol·L⁻¹ exogenous melatonin, and the relevant physiological indexes related with browning and quality were determinated at regular time during storage at 0±1 ℃. The results showed that melatonin treatment significantly (P<0.05) inhibited the increase of browning index, reduced the decay rate by 33.3%, significantly (P<0.05) delayed the decrease of firmness, total soluble solids, titratable acidity, and ascorbic acid content. The melatonin significantly (P<0.05） increased the activities of superoxide dismutase and catalase, significantly (P<0.05) inhibited the increase of lipoxygenase activity, O₂⁻· generation rate, H₂O₂, malondialdehyde content , and relative membrane permeability. Meanwhile, melatonin treatment significantly (P<0.05) delayed the increase of peroxidase, polyphenol oxidase, and phenylalanine ammonia lyase, and significantly (P<0.05) increased polyphenol content. These results indicated that the inhibiting fruit browning via exogenous melatonin treatment in sweet cherries might be closely associated with the improvement of antioxidant enzyme activities, the reduction of membrane lipid peroxidation degree, the maintenance of structural integrity of cell membrane and the inhibition of browning related enzyme activities.