Thrombus after one month of anticoagulation can be considered to be an old thrombus, and anticoagulation therapy needs to be continued to be given. Some thrombi need to be given anticoagulation therapy, such as deep vein thrombosis, left atrial thrombosis, etc. In the absence of endothelial damage to the blood vessel, a thrombus is to be considered as a red thrombus, and the main form of treatment is based on anticoagulation therapy. If the thrombus persists after more than one month of anticoagulation, consider an old thrombus. Obsolete thrombi require continued anticoagulation therapy, which remains effective in some patients, but in a minority of patients the thrombus may become mechanized and fail to dissolve completely. Adequate amounts of anticoagulants should be given during anticoagulation and the risk of bleeding should be assessed, with the option of anticoagulation with drugs such as rivaroxaban. Follow-up treatment with a physician is recommended to avoid delay.