Abstract: In order to further realize the waste utilization of PFP and reduce the waste of resources and environmental pollution, PFP pectin was extracted by ultrasonic assisted acid method and its antioxidant activity was studied. By investigating the effects of pH, solid-liquid ratio, ultrasonic time, ultrasonic power and ultrasonic temperature on the extraction ratio of PFP pectin, response surface optimization was carried out on the basis of single factor test to get the best extraction process, and acid method was used as the control. The effects of ultrasonic-assisted acid method on scavenging DPPH free radical (DPPH·), hydroxyl free radical (·OH) and superoxide anion free radical ( \textO_2^- ·) of PFP pectin were studied. The results showed that: The optimal extraction parameters of PFP pectin by ultrasonic assisted acid method were pH2.0, ultrasonic time 70 min, ultrasonic power 210 W, ultrasonic temperature 45 ℃, and the yield of pectin was 14.78%±0.21%. The scavenging rates of DPPH·, ·OH and \textO_2^- · were 60.96%±1.03%, 80.16%±1.78% and 59.13%±2.10%, which were higher than those of acid method.