The common diseases of lower extremity arterial ischemia include atherosclerotic occlusive disease, thrombo-occlusive vasculitis, vasculitis, arterial injury, arterial distress and arterial epicardial cystic disease, of which the first two are the most common. In the diagnosis of acute lower limb ischemia, special attention should be paid to the following issues in order to differentiate from several diseases: 1. Intermittent claudication should be distinguished from claudication caused by non-vascular lower limb pain (e.g. neurogenic claudication). 2. For patients with acute lower extremity ischemia such as sudden onset of lower extremity coldness, numbness, and resting pain, the history of claudication is the main basis for differentiation between arterial thrombosis and arterial embolism. 3, age and site of onset are the main points of differentiation between this disease and aortitis and thrombo-occlusive vasculitis, aortitis occurs in young women, mainly invading the aorta and its main branches, thrombo-occlusive vasculitis is mostly seen in young and strong men who smoke, mainly involving the middle and small arteries and veins of the limbs. It is often complicated by thrombophlebitis, with a slow progression of disease, no arterial wall calcification, no diabetes, hypertension, hyperlipidemia, etc. 4, Raynaud’s disease (signs): the prevalence of young women, often due to cold or emotional changes to stimulate the typical changes in finger skin color, mostly bilateral symmetry. A few patients can occur in the lower extremities or extremities. During the non-episode period, the color of the affected fingers (toes) is normal. 5, thrombo-occlusive vasculitis (thrombosis angiitis obliterans, TAO) is a different from atherosclerosis, segmental distribution of vascular inflammation, lesions mainly involving the distal segments of the extremities of small and medium-sized arteries, pathology is mainly characterized by the infiltration of inflammatory cells thrombus, and less often the involvement of the vessel wall.