The external jugular vein is a very important superficial vein of the head and neck, formed by the posterior branch of the posterior mandibular vein, the retroauricular vein and the occipital vein converging at the angle of the mandible, which runs down the surface of the sternocleidomastoid muscle, penetrates the deep fascia above the clavicle and injects into the subclavian vein or the angle of the vein. The role of the external jugular vein is mainly to collect venous blood from the head, scalp and face. The external jugular vein has a pair of valves at its end, but it cannot prevent the backflow of blood. The external jugular vein is often not visible in the normal standing or sitting position and may be slightly filled when lying down, but only in the lower 2/3 of the segment between the angle of the jaw and the superior clavicular rim. If there is poor reflux due to heart disease or superior vena cava obstruction, the jugular vein is filled when semi-recumbent, which means that the patient should pay attention to the heart or some other diseases caused by poor venous reflux.