Deep vein thrombosis is the abnormal clotting of blood in the deep veins and is a disorder of venous return in the lower extremities. Thrombosis mostly occurs in the braking state (especially in major orthopedic surgery). The causative factors are slow blood flow, venous wall damage and hypercoagulable state. After thrombosis, except for a few that can ablate on their own or be confined to the site of occurrence, most of them will spread to the deep vein trunk of the whole limb, and if they are not diagnosed and treated in time, most of them will evolve into the sequelae of thrombosis, which will affect the quality of life of patients for a long time; some patients may have pulmonary embolism as a complication, causing extremely serious consequences.