Carbon dioxide laser is a traditional laser with a history of 50 years ago, but the traditional laser has disadvantages such as large damage, long recovery time and many side effects because it does not have fractional mode. Fractional technology was introduced in 2006, and its theory originated from the theory of fractional photothermolysis proposed by Rox Anderson, an expert in photomedicine from Harvard University in 2004, which is an expansion and leap from the traditional theory of selective photothermolysis. The fractional laser has adjustable parameters, such as adjustable spot diameter, adjustable treatment density, adjustable treatment depth, and adjustable treatment energy, making it possible to obtain personalized treatment plans for different diseases and thus obtain the best results. The essence of fractional treatment is to achieve maximum efficacy while minimizing recovery time and side effects. The fractional CO2 laser is a gas laser, the principle of action is “focal photothermal action”, through the fractional laser to produce an array of tiny beams, after the action of the skin to form a number of three-dimensional columnar structure of the tiny thermal damage area, each tiny damage area is surrounded by undamaged normal tissue, its keratinocytes can quickly crawl, so that it heals quickly. It can make the collagen fibers and elastic fibers proliferate and rearrange, so that the content of type I and III collagen fibers is close to the normal ratio, so that the structure of the pathological scar tissue is changed, and gradually softens and regains elasticity. The main absorbing group is water, which is precisely the main component of the skin. It can cause the dermal collagen fibers to contract and denature when heated, and induce a trauma healing reaction in the dermis, resulting in the orderly deposition of collagen and promoting collagen proliferation, thus improving skin elasticity and reducing scarring. The clinical characteristics are: the efficacy of scar treatment is comparable to that of plastic surgery, but less invasive, shorter recovery time, less side effects, and more acceptable to patients.