Wet gangrene of the lower extremities is a clinical manifestation of lower extremity venous thrombosis, which refers to the abnormal clotting of venous blood in the deep veins of the lower extremities, blocking the lumen and resulting in venous return obstruction. However, lower extremity venous thrombosis is easily confused with certain lower extremity venous reflux disorders and limb ischemic diseases, so clinical attention should be paid to differentiation. So how to differential diagnosis, the following is explained. Differential diagnosis 1, primary lower limb deep vein valve insufficiency: this disease because of the lower limb deep vein valve free edge relaxation, sagging, valve leaflet can not be closely together, so that the venous blood completely to the distal limb backflow, causing deep venous hypertension and stasis, and make the traffic branch venous valve destruction, and the lower limb swelling and obvious superficial varicose veins. It is most common in people who work in standing position for a long time. The onset is insidious and relatively slow. These are not identical to lower extremity venous thrombosis. It is important to pay attention to differentiation. 2.Simple varicose veins of lower limbs: mostly seen in young and middle-aged men, mainly characterized by varicose veins of saphenous and small saphenous veins of lower limbs. There is a sense of heaviness and fatigue in the lower limbs, and there is rarely swelling, and only after long standing or activity, there is slight swelling in the calf and ankle, which disappears on its own after rest. In contrast, in the case of lower limb venous thrombosis, there is extensive swelling, obvious distension or severe pain in the lower limbs, and the secondary superficial venous anger and varicosities are also more significant and extensive. If necessary, ultrasound Doppler examination and lower limb venography, etc. can be performed to make a clear diagnosis. 3.Acute arterial embolism of lower limb: It is mostly caused by wind heart disease, coronary heart disease, atrial fibrillation, etc. Sudden occurrence of severe pain in the limb, with the finger end as the heavy, the affected limb is cold, pale, loss of sensation, limb wrinkling, shallow vein atrophy, and the arterial pulsation below the embolism plane disappears. Extensive gangrene of the limb may occur. Attention should be paid to the differentiation.