When it comes to measuring blood pressure, people will naturally roll up their sleeves and stretch out their arms. If anyone lifts up his pant leg and stretches out his foot and neck to measure blood pressure, he will definitely think that the doctor has made a mistake. In fact, to prevent and control atherosclerotic disease, we must pay attention to the ankle-brachial index (ABI). The so-called ankle-brachial index is the ratio of systolic pressure in the ankle to systolic pressure in the upper arm. It is an important data from the measurement of blood pressure in the lower extremities. For measurement, the systolic blood pressure in the upper arm and lower extremity ankle is measured in a standard supine position, using the highest systolic blood pressure in the ankle and upper arm, respectively. In normal subjects, ankle systolic pressure should be greater than or equal to arm systolic pressure, with a normal ratio range of 0.9-1.1, while an ankle-arm index less than or equal to 0.9 should be considered insufficient arterial blood supply to the lower extremities. The ankle-arm index is a simple, inexpensive and non-invasive screening test for peripheral arterial disease of the lower extremities. Currently, there is a great deal of knowledge about coronary heart disease and ischemic stroke, but there is a serious lack of knowledge about peripheral arterial disease. Most peripheral artery disease of the lower extremities is asymptomatic, but has a risk of death and disability. Data show that peripheral arterial disease of the lower extremities increases the morbidity and mortality of vascular disease by 5-6 times, and the 5-year mortality rate of patients with peripheral arterial disease of the lower extremities is approximately 30%, of which 75% die from cardiovascular disease. It is important to learn simple and easy screening test methods, early detection and early treatment is a good way to control lower extremity atherosclerosis occlusive disease.