Superfine grinding-assisted enzymatic extraction of soluble dietary fiber from Phaseolus Radiatus hull were studied, and the extraction conditions were optimized by two general rotary combination design. Then the properties were studied. The results showed that the superfine grinding could significantly improve the extraction rate of soluble dietary fiber of Phaseolus radiatus hull, when the particle size was 25～38 μm, and the enzymatic extraction of soluble dietary fiber were: ratio of solvent-to-solid 331 (mL/g), enzyme solution temperature, 60 ℃, ratio of enzyme-substrate 190 U/g, the enzymolysis time 2 h. Under this conditions, the yield of soluble dietary fiber reached 14.02%, the water holding capacity was 389%, the oil holding capacity was 142%, the expansion force was 2.67 mL/g, and the adsorption rate of sodium cholate was 30.29%.