Abstract: In order to reveal the influence of ultrasonic on the viscosity of potato starch paste,the viscosity of potato starch paste was investigated using a Brabender viscometer in different ultrasonic treatment conditions. The mechanism of viscosity changing was also analyzed by studying the changes of molecular weight and conformation of potato starch paste.The results showed that with the increasing of ultrasonic time and ultrasound intensity,the viscosity of potato starch paste was reduced.The smaller of the potato starch paste concentration,the greater the degree of viscosity was decreased.It was because that the ultrasonic vibration,shearing,jets and other effects of ultrasonic changed the rheology of potato starch paste from the molecular level.