Foot thrombosis in a 90-year-old man may be arterial thrombosis and venous thrombosis, which can be treated with anticoagulant drugs or interventional surgery. 1. Venous thrombosis: It is mainly caused by trauma, prolonged bed rest after surgery and other reasons. When venous thrombosis occurs in the feet, symptoms such as swelling, edema, increased skin temperature and pain on the back of the feet often occur. Usually, it is necessary to follow the doctor’s instruction to make subcutaneous injection of low molecular heparin, or use anticoagulants such as rivaroxaban and warfarin sodium tablets to improve the hypercoagulable state of the blood. 2. Atherosclerotic thrombosis: often accompanied by previous arterial stenosis, when the endothelium of the blood vessel is damaged, local thrombosis can be induced. Patients will show symptoms such as cold feet, fear of cold, pain, cyanosis of the skin, and in severe cases, blackening and necrosis of the skin. It is usually treated with low molecular heparin anticoagulation, sodium nitroprusside and other vasodilator drugs. If the condition is severe, interventional surgery can be considered. Patients should pay attention to rest, but also to check the nature and size of the thrombus, under the guidance of the doctor reasonable treatment. Follow the doctor’s instructions to use drugs, do not use drugs without authorization.