Abstract: Based on the single factor experiments,the Plackett-Burnman test design to determine the factors that had significant influence on the pectin extraction rate,and Box-Behnken test was further designed to optimize the extraction process of pectin in grapefruit peel. The results showed that the optimal process for extracting pectin from shaddock peel by enzymatic method combined with ultrasonic assisted acid method was as follows:Enzyme dosage 1.7%,enzymatic hydrolysis time 70 min,solid-liquid ratio 1:25 g/mL,extract pH2.0,ultrasonic power 260 W,the extraction temperature 83℃,and the extraction time 50 min.Under these conditions,the extraction rate of pectin in shaddock peel reached 27.01%±0.91%. Therefore,the enzymatic method,combined with ultrasonic assisted acid extraction of pectin in shaddock peel,could effectively increase the yield of pectin.