The disease starts rapidly, and the limbs and even lives are threatened after the onset of the disease, so early diagnosis and proper treatment in a matter of seconds are of utmost importance. 1. Acute arterial thrombosis is mostly caused by acute arterial ischemia due to secondary thrombosis on the basis of atherosclerosis. The key points of differential diagnosis are: ① The onset of the disease is less acute than arterial embolism, and the plane of pale and cold limbs is more vague. ②Past history of chronic arterial ischemia, such as intermittent claudication and dystrophic changes caused by insufficient arterial blood supply. ③Arteriogram shows extensive atherosclerosis, arterial wall is not smooth, irregular distortion, segmental stenosis or occlusion, there are more side branch formation and other manifestations, which coexist with arterial obstruction. 2, acute iliac-femoral vein thrombosis severe acute iliac-femoral vein thrombosis such as femoral cyanosis, extreme swelling of the limb on the arterial compression and strong arterial spasm, can cause arterial blood supply obstruction and distal arterial pulsation disappearance. However, clinical manifestations such as obvious swelling of the whole lower limb, compensatory dilation of superficial veins and normal or slightly elevated skin temperature are the characteristics of deep vein thrombosis, which can be distinguished from arterial embolism. Doppler auscultation can clearly hear the arterial pulsation, and the ankle/brachial index is usually 0.5. 3. Decreased cardiac blood displacement, acute myocardial infarction, congestive heart failure, sepsis, dehydration and severe trauma can cause a sharp decrease in cardiac blood displacement, increased secretion of vasopressin, systemic vasoconstriction, sharply reduced vascular perfusion in the extremities, cold extremities, and even skin efflorescence and weak or absent arterial pulsation. However, in addition to the manifestation of the heart itself disease, the limb syncope, etc. should involve the extremities at the same time. After the anti-shock, blood volume recovery, and effective control of the primary heart disease, the limb artery hypoperfusion condition is also relieved. 4. Clamped aneurysms are less common. Aortic coarctation aneurysms involving one or both iliac arteries can lead to acute ischemia of the arteries in the lower extremities. Usually the symptoms of a coarctation aneurysm are more prominent and the patient has hypertension, severe back or chest pain, and other symptoms. 5.Acute thrombosis of arterial or femoral aneurysm intra-luminal thrombosis of aneurysm leads to lumen occlusion, and a pulsating mass can be retrieved in the corresponding anatomical site. Duplex ultrasound can confirm the presence of aneurysm and intra-luminal thrombosis. 6.Femoral cyanosis is a special and serious type of acute thrombosis of the deep veins of the lower extremities. The limb is extremely swollen, bruised, superficial veins are dilated, and the dorsalis pedis and posterior tibial artery pulsations cannot be palpated. However, the limb remains warm.