Abstract: As a kind of high molecular weight carbohydrates composed by more than 10 glycoside bonded monosaccharides, polysaccharides not only are one of the essential substances to maintain basic life activity, but also have many important biological activities. However, the complex structural characteristics of polysaccharides not only restrict the study of structure-activity relationship of which, but also limit the design, construction and screening of functional polysaccharides based on their structural characteristics. Ultrasonic degradation of polysaccharide has become a hot spot all over the world due to two main aspects:on one hand, ultrasonic degradation has the advantage of high degradation efficiency, environmental protection and simple operation; on the other hand, the reaction conditions for polysaccharides degradation by ultrasonic wave are mild and could be controlled. Therefore, in the present review, the mechanisms and researches of polysaccharide degradation by ultrasonic wave in recent years are summarized. The advantages and disadvantages of ultrasonic degradation technology are introduced in detail. Meanwhile, effects of ultrasonic degradation on the structure, solubility, solution viscosity, rheological property and biological activity of polysaccharide were reported. Furthermore, the evolution of ultrasonic degradation technology is prospected, which provides a theoretical basis for the study and application of polysaccharide degradation by ultrasonic methods in the future.