In this study, ultrasound-assisted extraction of polyphenols from paeonia ostii oil peony seeds was used. On the basis of a single factor test, the material-liquid ratio, ultrasonic time, extraction temperature and ultrasonic power were set as independent variables, and the polyphenol yield was response value, optimize the extraction process of peony seed polyphenols by Box-Behnken response surface method. The results showed that the best conditions for extracting polyphenols from peony seeds were the ratio of material to liquid 1∶14 (g/mL), ultrasonic power 160 W, ultrasonic time 98 min, extraction temperature 57 ℃. Under the best technological conditions, the extraction rate of polyphenols in peony seeds was 33.38 mg/g. According to in vitro antioxidant experiments, peony seed polyphenols can effectively remove DPPH free radicals and ABTS free radicals, have a certain degree of antioxidant capacity, and can become a new natural antioxidant. This study is a comprehensive development of peony seed provide theoretical basis and reference.