Key points to differentiate diabetic foot gangrene from other gangrene: gangrene is the death of tissue cells. Etiology is often divided into circulatory gangrene, such as atherosclerotic gangrene, embolic gangrene, thrombo-occlusive vasculitis, gangrene caused by Raynaud’s disease, neurotrophic gangrene, diabetic gangrene, mechanical, physical, chemical, injury and infectious gangrene. Diabetic foot gangrene is difficult to distinguish from other gangrene by pathological changes and the nature and extent of gangrene alone. Diabetic vasculopathy and neuropathy are the basic causes of diabetic foot comorbidity. Diabetic feet are particularly susceptible to vascular and neuropathy, and diabetic vasculopathy and neuropathy interact to cause a range of clinical foot conditions, including toe disease, callus formation, skin damage and foot ulcers, and musculoskeletal lesions leading to foot deformities. Diabetics are often susceptible to trauma due to neuropathy leading to foot dissipation or decompensation, and minor trauma can quickly lead to ulceration, infection and gangrene, resulting in the eventual necessity of amputation. The incidence of diabetic foot has increased significantly. Laboratory tests for diabetes such as urine glucose, blood glucose, oral glucose tolerance test, etc. 2, ischemic examination (1) lower extremity posture test: diabetic foot patients’ skin is visibly pale after elevating the lower extremity for 30-60 seconds, and the middle of the limb is seen to be purplish after dropping. If the venous filling time (time for the skin of the foot to turn from pale to red) is more than 15 seconds, it means that the blood supply to the lower limb is obviously insufficient. (2) Arterial palpation of the lower extremity: the national artery and the dorsalis pedis artery can be palpated at the fossa of the country (the fossa behind the knee joint) and the dorsalis pedis, and the artery may be weakened or even disappear in patients with diabetic foot. (3) Limb hemogram: It can understand the blood supply and vascular elasticity of the limbs, but its accuracy is not good. (4) Ultrasound examination: color ultrasound Dappler is commonly used to examine the femoral artery, national artery and dorsalis pedis artery. It can be directly observed and quantitatively located and analyzed, and its perceptibility, specificity and accuracy are better, and it is a non-invasive examination method. (5) Arteriography: It can understand the scope of lower limb vascular lesions, blood flow distribution and the presence of collateral circulation. However, this method is an invasive examination, which can aggravate the arterial spasm and make the blood supply to the limb incomplete, and is generally used only for positioning examination before limb-lifting surgery. Microcirculation examination: Generally, the microcirculation changes in the finger nail wrinkles of diabetic patients are directly observed through the in vivo microscope, and the microcirculation abnormalities often suggest microangiopathy. 4, electrophysiological examination: the application of nerve conduction velocity electromyography examination, can be early detection of diabetic peripheral neuropathy. Diabetic peripheral neuropathy is an important factor in the development of diabetic foot. 5.X-ray examination: calcification of the arterial wall, osteoporosis and destruction, osteomyelitis and osteoarthrosis can be found, which are generally used as routine examinations.