Abstract: In order to explore the change rules of main components and antioxidant activity in the natural fermentation process of black chokeberry Jiaosu, the natural fermentation was carried out under 28 ℃ airtight container for 90 days. During the fermentation process, the physicochemical indexes and bioactive substances including reducing sugar, total soluble solids (TSS), alcohol, total acid, total polyphenols, total flavonoids, anthocyanins and superoxide dismutase (SOD) in fermentation broth were estimated. DPPH free radical, ABTS⁺ free radical, hydroxyl free radical scavenging capacity, total antioxidant capacity and total reducing power were used to comprehensively evaluate its antioxidant activity in vitro, Pearson's correlation analysis was also performed to further clarify the correlation between main components and antioxidant activity. The results showed that the contents of reducing sugar, TSS, total acids and anthocyanins in black chokeberry Jiaosu showed a continuous decreasing trend during natural fermentation, the alcoholic content continued to increase and gradually stabilized, while the contents of total polyphenols, total flavonoids and SOD enzyme activity increased first and then decreased. The highest values of total polyphenols, total flavonoids and SOD enzyme activity were 4.99 mg/mL, 269.68 mg/L and 5151.80 U/mL, respectively. The antioxidant activity of the Jiaosu after fermentation showed a peak-shaped change, which was significantly higher than that of unfermented sample (P<0.05). The maximum values of its scavenging rate for DPPH radical, ABTS⁺ radical and hydroxyl radical, total antioxidant capacity and total reducing power were 65.78%, 85.06%, 94.22%, 750.48 U/mL and 1.014, respectively. The results of correlation analysis showed that alcohol content, total polyphenols, total flavonoids and SOD were significantly positively correlated with antioxidant activity (P<0.05), while reducing sugars, TSS and total acids were significantly negatively correlated with antioxidant activity (P<0.05). The results of this experiment provide a theoretical basis for improving the product quality and industrial production of black chokeberry Jiaosu.