Abstract:The shape， size and size distribution of ice crystal in the crystallization prcocess and the thawing time cluring the thawing process are the main factors that influencing the qualities of frozen food. Ultrasonic as－ sisted refrigeration technology as a new refrigeration technology had been extensively studied， and the result showed that the ultrasonic had a positive impact on crystallization process and thawing process. This paper elu－ cidated mechanism of ultrasonic assisted refrigeration technology during the formation of ice crystal， mainly re－ lated to the effects of ultrasonic on nucleation， size and size distribution of ice crystal； introduced the applica－ tions of ultrasonic in frozen food from respects of freezing， thawing and non-destructive test.