Diabetic gangrene occurs mostly in middle-aged and elderly people; more men than women, with a male to female ratio of 3:2; the average duration of diabetes mellitus is about 10 years, and gangrene is common in the lower extremities, accounting for 92.5%, and rare in the upper extremities, accounting for about 7.5%; unilateral onset accounts for about 80%, and bilateral onset accounts for about 20%; simultaneous gangrene of the toes and soles is common, accounting for 77.5%; simultaneous gangrene of the toes and lower legs accounts for 5%, and gangrene of the lower legs only accounts for 5 percent; toe or finger onset accounted for 12.5 percent. Diabetic foot is a common complication of diabetes and can be very harmful to the health of the patient. In the case of dry diabetic gangrene, there are symptoms of blackening. To find out why diabetic foot appears black? To understand this first, we must first explain dry gangrene of the diabetic foot. Diabetic foot disease is divided into wet gangrene, dry gangrene and mixed gangrene, of which dry gangrene is mostly seen at the ends of the extremities, such as atherosclerosis, thrombo-occlusive vasculitis and frostbite and other disorders. At this time, arterial obstruction and venous return flow is smooth, so the necrotic tissue has less water, plus the body surface moisture is easy to evaporate, resulting in a dry and crumpled lesion, dark brown, and there is a clear line of demarcation between the surrounding healthy tissue.