Gangrene can be divided into three types: dry gangrene, wet gangrene and gas gangrene, mostly caused by tissue ischemic necrosis secondary to infection by corrosive bacteria, which can appear as local tissue necrosis, blackening and other changes. Patients should pay attention to the care of gangrenous limbs, keep dry, hygienic, if secondary infection, fever and other symptoms, should promptly seek medical attention. 1, dry gangrene: common in the ends of the limbs, mostly due to atherosclerosis, thrombo-occlusive vasculitis caused by the smooth venous return and arterial obstruction, resulting in water loss. The lesion is dry, solid and wrinkled, dark brown, with a white surface on the affected area, and is felt as dull pain and cold. Patients should be treated systemically, using insulin to control blood sugar, timely correction of hypoproteinemia, electrolyte disorders, and timely excision of infected necrotic lesions; 2. Wet gangrene: mostly occurs in organs that are connected to the outside world, such as the lungs, intestines, and appendix, where the necrotic tissue contains more water and is severely infected with spoilage bacteria, with significant local swelling, dark green or black. Due to the rapid development of lesions and more diffuse inflammation, there is no obvious demarcation line between necrotic tissue and healthy tissue. Patients should choose antibiotics to control the infection, such as ampicillin, and surgical debridement and intervention if necessary; 3. Gas gangrene: often caused by anaerobic bacterial infections, such as P. aeruginosa and Clostridium perfringens, which may lead to hemolysis, edema, and tissue necrosis. In addition to the occurrence of necrosis, a large amount of gas is produced, which makes the necrotic area feel like twisted hair when pressed. The onset of disease may be sudden and in severe cases may be disabling and life-threatening. Intravenous penicillin should be administered and surgical debridement should be performed as soon as possible; severe patients may require amputation.