Abstract: In this study, foodborne microorganisms capable of fermenting and decomposing soy proteins were screened, and molecular weight analysis was performed for the peptides produced during decomposition. Subsequently, oligopeptides were obtained via isolation and purification, and their antioxidant activities were studied. The experiment results showed that a PZ1 strain was isolated from homemade kimchi and identified as Lactococcus lactis based on morphology and 16S rDNA sequence analysis. Whole genome analysis showed that the PZ1 strain contained a variety of peptidases and protease genes that had the potential to decompose proteins. Soybean proteins were then fermented by PZ1, and the polypeptides produced during fermentation were analyzed via gel permeation chromatography, revealing that 85% of polypeptides had a molecular weight below 1000 Da. The oligopeptides with molecular weight 300～1000 Da were obtained via ultrafiltration purification, and their antioxidant activity was studied. The oligopeptides demonstrated a good scavenging effect on DPPH, hydroxyl (·OH), and superoxide anion (O₂⁻·) radicals, at an oligopeptide concentration of 2 mg/mL, the clearance rates were 79.31%, 78.27%, and 84.62%, respectively. Therefore, L. lactis PZ1 could degrade soybean protein efficiently and could be used as a probiotic for developing functional soybean products.