Abstract: Objective:To optimize the preparation of konjac oligo-glucomannan in semi-drying enzymatic hydrolysis method.Method:Based on one- factor- at- a- time experiments, a three- variable, three- level Box- Behnken experimental design was applied to establish a quadratic polynomial model for the hydrolysis rate of konjac glucomannan as a function of enzymolysis time, beta mannan activity and Konjac Glucomannan-to-buffer solution ratio;and then the antioxidation of its product was determined.Results:the optimal reaction condition were pH6, reaction temperature of 55℃, reaction time of 4.2h, konjac glucomannan-to-buffer solution ratio of 1∶1.63 and beta mannan activity of 1500U /g;The IC 50 to·OH and O- 2 ·of konjac oligo-glucomannan prepared in this method were 0.4331、15.7mg /mL, and its reducing ability was 73.82% of V C at the same concentration.Conclusion:the experimental hydrolysis rate of konjac glucomannan obtained under these conditions was 52.67%, which was consistent with the theoretical value, and the optimized result was reliable and could be used in practice;The product had great antioxidant capacity.