There may be several reasons for patients with malignant tumor to have blood in urine: 1. metastasis in urinary system, metastasis in kidney, bladder, ureter, etc. may occur in late stage of malignant tumor patients, and metastasis destroying blood vessels will cause blood in urine, and malignant tumor in urinary system itself will also cause blood in urine. 2. side effect of chemotherapy, patients may have coagulation dysfunction after chemotherapy, which is caused by damage to coagulation system by chemotherapy drugs. Coagulation disorder will lead to spontaneous bleeding and blood in urine. In addition, chemotherapy leads to suppression of bone marrow hematopoietic function, decrease in white blood cell count, decrease in body resistance and urinary tract infection; decrease in platelet count and hemostatic disorder, both of which can lead to urinary tract bleeding and formation of hematuria. For example, cyclophosphamide can lead to hemorrhagic cystitis, the common clinical manifestation of which is blood in urine. 3, other rare causes, such as malignant tumor patients with extremely poor body resistance, easily complicated by special bacterial infections, among which tuberculosis infection is more common and urinary tract tuberculosis may lead to blood in urine.