Smoking increases the risk of blood clots in the legs and may cause thrombosis in the lower extremities. After long-term smoking, nicotine, nicotine and other harmful substances in tobacco can damage the endothelium of blood vessels, blood vessel walls, and easily cause thrombosis. It can also stimulate blood vessels to trigger vasoconstriction and spasm, which can trigger vascular atherosclerosis. Long-term chronic vascular damage can trigger chronic vasculitis, blood vessels with endothelial cells and fibroblasts proliferation, lymphocyte infiltration, inflammation subsides, there can be thrombus mechanization, may cause thromboembolic vasculitis, to the lower extremity blood vessels are more common, intermittent claudication or resting pain can occur. Smoking not only increases the risk of lower extremity thrombosis, but also increases the incidence of respiratory diseases, it is recommended to quit smoking, if you feel unwell, consult a doctor in a timely manner, and standardize treatment under the guidance of a professional doctor.