Abstract: Objective: To improve the early diagnosis of primary malignant lymphoma of the urinary bladder. Methods: 4 cases of primary malignant lymphoma of the urinary bladder were immunohistochemically analysed for the phenotype and the clinical presentations、treatment and prognosis were also discussed. Results: The most common symptom is haematuria、dysuria and frequency. Cystoscopic examination showed the tumor as pachy or hemisphered protrudings but the mucosa was usually intact. Immunohistochemically the tumors all showed B cell phenotype, including three as low grade mucosa-associated lymphoid tissue lyphoma（CD20⁺/CD10^-/CD5^-） and one as follicular center cell lyphoma（CD20⁺/CD10⁺）. The survival of patient rang from 3~7 years. Conclusion: malignant lymphoma of urinary bladder were predominantly B cell type and most of them were low grade mucosa-associated lymphoid tissue lymphoma. Diagnosis was established by histological examination. The treatment of the patients include Surgical resection with or without radiotherapy and chemotherapy. The prognosis was thought to be favorable.