Urine is black for the following reasons: First, acute hemolysis, mainly in the blood transfusion blood type does not match or malignant malaria hemolysis phenomenon, resulting in the formation of hemoglobinuria, so that the urine is soy sauce color. Second, melanuria, mainly by the lack of enzyme oxidizing melanuria in the body, resulting in the presence of melanuria in the urine, and the urine is black under the action of melanuria. Third, acute jaundice hepatitis, when the body’s bile excretion is impaired, resulting in increased bilirubin in the blood, so that the urine bilirubin increases, resulting in black urine. Fourth, the body suffers from bladder tumors, kidney tumors, systemic trauma, prostate cancer, urinary tract infection, urinary tract trauma and other reasons are also prone to black urine, when the urine is black, we should go to the hospital in a timely manner to carry out examinations, to identify the cause of the disease in the doctor’s guidance under the symptomatic treatment with medication, usually drink plenty of water, urinate diligently, and eat more fresh fruits and vegetables.