This paper used single factor and response surface analysis to optimize the fermentation process of peony seed meal soy sauce, and the antioxidant activity of peony seed meal soy sauce was studied. The result showed that the establishment of regression model reflects the relationship between the content of amino nitrogen and fermentation temperature, fermentation time and salinity of peony seed meal soy sauce. The optimum fermentation conditions of peony seed meal soy sauce were fermentation temperature of 45.5 ℃, fermentation time of 18 days, and salinity of 12%. Under the conditions, the content of amino nitrogen in peony seed meal soy sauce was 0.616 g/100 mL. According to the oxidation experiments in vitro, peony seed meal soy sauce under high temperature and high-pressure sterilization had better scavenging ability to DPPH free radicals, and the scavenging rate can reach 94.19%.