Swelling of legs in the afternoon is mainly due to localized swelling of the lower limbs after prolonged standing or exertion, mostly due to diseases of vascular origin, the most common diseases are lower limb venous thrombosis and simple venous insufficiency of the lower limbs. The most common diseases are lower extremity venous thrombosis and simple lower extremity venous insufficiency. Lower extremity venous thrombosis occurs when the thrombus blocks the pathway of blood flow after standing or sitting for a long time, which causes limitation of venous blood flow in the lower extremity and swelling of the lower extremity. Simple venous insufficiency of the lower limbs is mainly due to the thin wall of the venous blood vessels, weakened elasticity, valvular insufficiency, blood reflux occurs, and the refluxed blood is stagnated in the calves, and swelling of the calves occurs in the afternoon. Therefore, when the condition of afternoon leg swelling occurs, it is necessary to consider the vascular causes of leg swelling, it is recommended to improve the lower extremity venous ultrasound examination in the vascular surgery clinic, to make clear whether the cause of leg swelling is thrombus, or simple venous insufficiency, and can be under the guidance of specialists to actively treat the symptoms.