The sweet potato liquefaction juice was used as raw material. Ultrasound was employed in the processing of glucoamylase enzymatic digestion. The influence of ultrasonic power, frequency, enzymolysis temperature and enzyme dosage on glucoamylase enzymolysis reaction were studied by using single factor experiment and orthogonal test. The optimum condition of glucoamylase enzymolysis reaction was obtained. Research results indicated that, under the optimal conditions of ultrasonic power of 420 W, frequency of 45 kHz, enzymolysis temperature of 65℃ and enzyme dosage of 150 U/g, the reducing sugar content arrived to 1.541mg/mL, which increased by 24.78% compared with control. 