The invention relates to the field of washing of marine products, in particular to a washing method for oysters belonging to shellfishes. The method comprises the followings steps: flushing oysters tobe washed with water; removing dead oysters and impurities; filling the oysters and water into a container; immerging the container in an ultrasonic washing cylinder, and adjusting the proportion ofoysters to water; carrying out ultrasonic washing; and taking the oysters out of the container. The ultrasonic medium for the ultrasonic washing is tap water or sea water, and the temperature of the medium is below 25 DEG C; the ultrasonic frequency ranges from 20 to 50 kHz; and the time for the ultrasonic treatment is 4-8 minutes. The invention provides an ultrasonic washing method and also particullarlly provides the technical requirements for the ultrasonic washing. The method has the advantages of favorable washing effect, high cleanliness, high speed, high efficiency and water resource saving, and basically keeps the oysters alive. The method is simple and systematic, not only solves the washing problems during the processing of the oysters, but also ensures the livability and ediblesafety of shellfishes in the washing course.