To develop new functional foods with higher nutritional value and antioxidant function, this paper performed probiotic fermentation on Actinidia arguta juice to investigate its effects on major bioactive components, antioxidant activity, and metabolites. The results showed that probiotic fermentation significantly increased bioactive components in A. arguta: total phenols (4.52 mg•g-1), flavonoids (4.12 mg•g-1), and ascorbic acid (80.38 mg/100 g) all peaked at 48 h, representing increases of by 25.91%, 32.90%, and 36.24%, respectively, compared with pre-fermentation levels. Antioxidant properties were also enhanced, with the DPPH radical scavenging rate increasing to 87.55%, and both the hydroxyl radical and ABTS+ scavenging rates increasing to more than 50% compared with pre-fermentation levels. Metabolomics analysis identified 446 significant differential metabolites, mainly lipid and lipid-like molecules, organic oxides, and organic acids. Lipid molecules can be efficiently absorbed by human microflora and used as an energy source, while organic acids promote trace-element absorption and improve appetite and digestion. Using A. arguta as a substrate for probiotic fermentation enhances antioxidant capacity and improves flavor and nutritional composition through metabolites production. This provides a scientific method for developing high-quality probiotic-fermented juices and a theoretical basis for their industrial production.