The black color of the patient’s urine is considered to be caused by the following reasons: First, it should be considered to be acute hemolysis, when hemolysis occurs the patient’s urine color will appear soy sauce, the appearance of the color is black or black-red, mostly seen in exogenous blood input or acute allergy. Second, patients with urinary bleeding may also cause this phenomenon. Patients with urinary bleeding will form black urine if blood is deposited in the bladder and hemoglobin is sulfated. Thirdly, it should be considered as caused by special infections, such as rectal urethral fistula, which can cause contamination of the rectum into the urethra, and foul matter mixed in the urine will cause an increase in precipitation, thus staining the urine black. The above is the common specific reasons for the blackness of the urine of patients, it is recommended that patients with symptoms should promptly go to the regular hospital urology department for relevant examinations to clarify the diagnosis and further treatment under the guidance of the doctor.