If the foot is black and purple, it is necessary to clarify whether the foot has been injured before, if it has been injured, it is usually associated with the injury; if there is no injury experience, it is necessary to consider whether it is caused by other disease factors, and it is necessary to explain the medical history to the doctor when seeking medical attention. Most of the black-purple phenomenon of the foot is due to direct external force on the foot, injury to the local fascial tissue or muscle soft tissue, and did not take the correct treatment measures, but massage, rubbing, etc. to the injured parts, or did not limit the activities, thus aggravating the degree of local injury, and then the phenomenon of black-purple feet. It is also possible that the external force has caused some damage to the local capillaries, resulting in capillary bleeding, which is not absorbed in time and gradually forms a subcutaneous hematoma or stasis of blood, giving a blackish-purple appearance. In these cases, if there is no skin damage and the symptoms are mild, cold compresses can be applied to stop the bleeding at an early stage and hot compresses can be applied to reduce the swelling after stopping the bleeding to promote the absorption of the bruises. If the bleeding continues or is accompanied by serious conditions such as fractures, symptomatic medication or immobilization is usually required. Lower extremity deep vein thrombosis is a common disease that causes blackish purple color of the feet, mostly occurs in the lower leg deep vein plaque and thrombosis, due to the obstruction of venous blood return to the feet, resulting in a blackish purple color of the skin of the feet. In addition, deep vein thrombosis in the lower extremities can also cause significant swelling, decreased skin temperature, and restricted movement in the lower extremities. After the cause is clear, medication such as Diosmin tablets and Mizarin tablets are needed to promote venous reflux, and varicose veins stockings should be worn.