Abstract: Taking purple yam as the experimental material, the optimum conditions of ultrasonic-assisted extraction of procyanidins from purple yam were studied and their antioxidant activities in vitro were evaluated.On the basis of single factor test, response surface methodology was used to optimize the extraction yield of proanthocyanidins. Results showed the optimum condition were as follows: ethanol volume fraction 70%, ultrasonic time 30 min, liquid-material ratio 19∶ 1 ( m L/g) , extraction temperature 59 ℃, ultrasonic power 220 W. Under such conditions, the yield of procyanidins was 92.47 mg/g.Procyanidins from purple yam showed significant antioxidant capacity, and half inhibition concentrations ( IC₅₀) of DPPH·and that of·OH were0.182 mg/m L and 0.289 mg/m L respectively, the scavenging abilities and reducing power were stronger than vitamin C.