China generally adopts the three degrees and four divisions, that is, according to the depth of skin burns are divided into shallow Ⅰ degree, shallow Ⅱ degree, deep Ⅱ degree, Ⅲ degree. Those deep to the muscle and bone are still calculated according to Ⅲ degree. Clinically, for the convenience of expression, Ⅰ degree and shallow Ⅱ degree are called shallow burns, and deep Ⅱ degree and Ⅲ degree are called deep burns. 1, Ⅰ degree burns: called erythematous burns, only the superficial epidermal layer DD keratin layer, hyaline layer, granular layer or injury to the spiny layer, but the occurrence layer is alive. Local redness, slight swelling, burning pain, no blistering. 3-5 days to heal, fine flakes, no scarring. 2.Second-degree burns: also called blistering burns. Shallow degree II: destruction of part of the hair growth layer or dermal papilla layer. The wounded area is red, swollen and painful, with blisters or separation of epidermis and dermis, containing plasma-like yellow liquid, and the wound surface is bright red, moist, painful and exuding after removal of blisters. If there is no infection, the wound heals in 1-2 weeks. The epithelial regeneration relies on the residual hair growth layer or hair follicle epithelial cells, and traces or pigmentation are visible in the short term after healing, but no scarring is left. Deep degree II: In addition to the epidermis and all dermal papillae layer burned, the dermal reticular layer is partially involved, and the hair follicles and sweat glands located in the deep dermis are still alive. After rupture of the blistering skin or removal of the putrefied skin, the trauma surface is white-on-red, red-white or fine embolized vascular network is visible, the trauma surface has much exudation, edema is obvious, the pain is dull, and the hair-pulling test is slightly painful. Wound healing requires a process of necrotic tissue removal, shedding or healing under the scab. The residual hair follicles, sweat glands and water epithelial cells gradually grow to epithelialize the trauma, which generally takes 18 to 23-4 weeks to heal and can leave scar hyperplasia and contracture deformity. 3.Ⅲ degree burns: also known as crusty burns. The epidermis and dermis of the skin are destroyed, deep into the subcutaneous tissue, and even muscle and bone are also damaged. The layer of necrotic tissue formed on the trauma is called scab, pale white, yellow-white, burnt yellow or burnt black, dry and hard scab can be leather-like, scab can be seen on the embolized subcutaneous venous network in the form of dendrites, trauma pain disappears, plucking test easy to pull out without pain. The Ⅲ degree trauma of scalding can be pale and moist. In 2 to 4 weeks after the injury, the scab dissolves and falls off, forming granulation trauma, and the larger ones need skin implants to heal, and often leave scar contracture deformity. The distinction between Ⅰ, Ⅱ and Ⅲ degree burns by flushing, blistering and scorching captures the main characteristics of burn depth identification, which is easy to understand and remember. Because the thickness of the skin varies greatly in different individuals with different parts of the body, and also varies with different ages, deep Ⅱ and Ⅲ degree burns are sometimes difficult to distinguish accurately in the early stages. It can be verified during the treatment process, and generally after 2-3 weeks it will be clear whether the trauma belongs to deep II or III degree. The thin skin of pediatric patients often makes it easy to mistake Ⅲ degree burns for deep Ⅱ degree burns, and special attention should be paid to this. In 2001, at the National Burn Conference, the experts proposed to revise the method of estimating the depth of burns. 2002, the expanded meeting of the Standing Committee of the Society of Burn Surgery of the Chinese Medical Association was held for consideration. After that, the “Clinical Diagnostic and Treatment Routine (Burns Division)” edited by the Chinese Medical Association formally changed the third degree and fourth degree into the fourth degree and fifth degree. In other words, the original three degrees were further divided into three degrees and four degrees, with degree III being different degrees of skin damage and degree IV being deeper burns beyond degree III, with the degree of damage reaching seriously below the deep fascia.