The principle of ultrasonic cleaning is that the high-frequency oscillation signal issued by the ultrasonic generator is converted into high-frequency mechanical oscillation by the transducer and transmitted to the medium - cleaning solvent. The radiation of the ultrasonic wave in the dense phase of cleaning liquid is radiated forward, so that the liquid flows and generates tens of thousands of tiny bubbles. These bubbles form and grow in the negative pressure area of ultrasonic longitudinal propagation, and close quickly in the positive pressure area. In this process, which is called "cavitation" effect, the bubble closure can form an instant high pressure of more than 1000 air pressure, and the continuous production of instant high pressure is like a series of small "explosion" constantly impact the surface of the object, so that the dirt in the surface and cracks in the object quickly peel off, so as to achieve the purpose of object surface purification.