Ultrasonic knife is known as High Intensity Focused Ultrasound (HIFU), which has become one of the most important means to combat skin laxity due to its precise effect, high safety and long maintenance effect. Ultrasonic knife can reach the SMAS fascia layer, which can reconstruct a strong and powerful skin support network, with precise energy positioning and high temperature, which can effectively stimulate fiber contraction and collagen growth at the treatment level without damaging the epidermal tissue. The specific effects are as follows: 1. Reshape youthful contours: lift sagging parts, get rid of excess facial fat, smooth lines, and reshape three-dimensional tight facial contours; 2. Smooth wrinkles: eliminate forehead lines, eye lines, decree lines, mouth lines, lighten neck lines, and prevent neck aging; 3. Lift sagging tissues: tighten eye bags, double chin, sagging cheeks, sagging eye corners, and enhance eye and eyebrow lines; 4. 4, restore skin elasticity: stimulate the restructuring and renewal of collagen, making the skin delicate, shiny and elastic. It should be noted that although ultrasonic knife has a more comprehensive function, but the effect is not immediate, about six months after treatment to see the obvious effect, and the doctor’s professional technical level has certain requirements, candidates should go to a regular hospital to receive treatment.