Abstract: In order to compare the antioxidant properties of three walnut by-product polyphenol extracts,walnut green skin,walnut protein and walnut shells were used as raw materials,the extraction rate of polyphenols and the reducing power were measured together with the removal rate of DPPH free radicals,hydroxyl radicals and superoxide anion radicals,by ultrasonic extraction with water and different proportions of methanol and ethanol.The results showed that the extraction rate of polyphenols was the highest by using 40% ethanol as the extracting agent.The three kinds of walnut by-product polyphenol extracts had anti-oxidation ability in vitro,and the order showed as walnut green skin > walnut protein > walnut shell. The alcohol extract of the walnut green skin had good antioxidant properties and thus could be an antioxidant.