Abstract: In this paper,the ultrasonic-assisted extraction of polyphenols from pomegranate root bank was discussed and its antioxidant activity in vitro was evaluated. With the yield of polyphenols as an evaluation index,Plackett-Burman (PB) was applied to optimize the significant factors,after which Central Composite Design (CCD) was adopted to optimize the process conditions,then the antioxidant activity was evaluated by detecting the scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical and 2,2'-amino-di (2-ethyl-benzothiazolinc sulphonic acid-6) ammonium salt (ABTS). Results showed that:60% for ethanol concentration,49℃ for ultrasonic temperature and 34 min for ultrasonic time,the yield of polyphenols was 1.643%,which was close to predicted value. The clearance rate of DPPH free radical and ABTS were 70.3% and 65.7%,IC₅₀ were 71.166 μg/mL and 163.319 μg/mL,and there was a positive correlation between scavenging capacity and concentration of polyphenols. Ultrasonic assisted extraction of polyphenols from pomegranate root bark was feasible and reliable,Pomegranate root bark polyphenols had certain antioxidant capacity in vitro.