Abstract: Radioimmunotherapy, a kind of internal radiation therapy, can achieve high performance and low toxicity by fewer monoclonal antibodies couple radioactive nuclides, created sufficient ionization biologic effect on tumor. Non-Hodgkin lymphoma (NHL) is the most common hematological malignancy. Most of them are B cell lymphomas. CD20 is the best target of radioimmunotherapy on B cell-NHL. Clinical trials indicate ¹³¹Ⅰ-rituximab is effective on B cell-NHL, while many problems are existed. Approaches are under investigation to improve outcomes in patients with B cell-NHL.