Abstract: In this study,the optimal extraction process of soluble antioxidant dietary fiber(SADF)from sponge layer of Guanxipomelo peels was studied to realize comprehensive utilization of honey-pomelo waste and reduce resource waste.Guanxi honey-pomelo peels were selected as raw material,and the SADF from the spongy layer of the peels was extracted by ultrasonic-assistedenzymatic method. Based on the single factor experiment which investigated the influence of ultrasonic action time,solid-liquid ratio,cellulase dosage,cellulase temperature,as well as cellulase action time on both extraction yield and antioxidant activity of SADF,Box-Benhnken dual-response surface optimization experiment characterized with 3 levels and 3 factors,combined with Matlabanalysis was carried out. The optimal technological condition was determined as follows: ultrasonic pre-treatment for 30 min,solid-liquid ratio of 1∶55 g/mL(1∶53~1∶55 g/mL),cellulase dosage of 3%,cellulase action temperature of 50 ℃(48~50 ℃),cellulase action time of 90 min(The upper limit C=90 min). On this condition,the theoretical extraction yield and hydroxyl radical clearance rate of SADF from Guanxi honey-pomelo peels can reach 31.40%(25.12%~31.40%)and 66.16%(51.50%~66.16%),respectively,which showed no significant difference between the actual value(extraction yield: 32.82%±0.33%,clearance rate: 64.43%±1.88%)(P>0.05). It can be seen that the SADF of the sponge layer from pomelo peels obtained under the optimized process conditions by Box-Benhnken combined with Matlab was of better extraction yield and hydroxyl radical clearance rate,so that providing a new idea for the extraction and application of functional raw materials.