Objective: To investigate the effects of preharvest spraying of chitosan oligosaccharides (COS) on the antioxidant metabolism and storage quality of postharvest prunes. Methods: Xinjiang ｀French' prunes were used as test material， and different concentrations of COS (0.5， 1.0， 2.0 g/L) were sprayed during fruit set， expansion， color change and ripening， respectively. The postharvest fruits were stored at a temperature of (1.0±1) ℃ and a relative humidity of 90%-95% for 90 d， and the relevant indexes were determined by sampling every 15 d. The results were summarized as follows Samples were taken every 15 d and related indexes were measured. Results: Pre-harvest application of COS maintained higher firmness， titratable acidity， and soluble solids content in plum fruits during storage. It effectively suppressed surface color darkening， significantly reduced respiratory intensity and weight loss rate， with superior sensory quality compared to the control group. Among the treatments， the 1.0 g/L COS group exhibited the most favorable effects: 57.24% higher firmness， 115.38% higher titratable acidity， 19.38% higher soluble solids content， 22.09% lower respiration rate， and 48.42% lower weight loss compared to the control. Compared with the control group， pre-harvest spraying with 1.0 g/L COS promoted the accumulation of ascorbic acid (ASA) and glutathione (GSH) content. Increased levels of superoxide dismutase (SOD)， catalase (CAT)， peroxidase (POD)， ascorbate peroxidase (APX)， glutathione reductase (GR) activity， reduced the rate of superoxide anion (O₂-·) production and hydrogen peroxide (H2O₂) content， and inhibited the accumulation of malondialdehyde (MDA) content and the increase of cell membrane. Conclusion: The preharvest spraying of COS can regulate the antioxidant metabolism of prune fruits during storage and maintain the storage quality of prune fruits.

chitosan oligosaccharides  /  pre-harvest spraying  /  plums  /  antioxidant metabolism  /  storage quality