The site of thoracic duct injection is the left venous angle. The thoracic duct originates from the celiac pond in front of the second and third vertebrae of the lumbar spine, it collects the lymph from the abdominal trunk, intestinal trunk and both lower extremities, then passes through the esophageal fissure, travels between the aorta and the odd vein, after reaching the top of the chest upward, passes above the esophagus to the neck, then bends downward and returns to the left venous angle after injecting into the left venous angle, which is the whole journey of the thoracic duct. The lymphatic fluid of the left hemithorax, abdominal cavity and both lower extremities is collected in the thoracic duct, and its pathological significance is that when the patient has a tumor on the left side, it can spread to the upper left clavicle.