Although the ultrasonic knife is called a knife, its principle is to release a high-intensity focused ultrasonic wave (High Intensity Focused Ultrasound), which is a technology developed based on ultrasonic waves. Focusing and other physical properties, the external energy ultrasound penetrates normal tissues without damage, and accurately focuses on the beauty treatment area in the body (the corresponding positions of the skin dermis, basal layer, and SMAS fascia layer, and the surrounding tissues are not in focus because they are not in focus. Affected), in an instant within 0.5 seconds, a thermal condensation point of 65 ° C ~ 70 ° C will be generated, so that the tissue cells in the target area will immediately produce a protein coagulation reaction, and a pulling force will be generated around the freezing point.