Abstract: Objective 　To evaluate MRI in diagnosis and differentiation of primary cent ral nervous system (CNS) lymphoma. Methods 　MRI features in 7 patients with pathologically proved primary CNS lymphoma were ret rospectively analyzed. Results 　Allcases were pathologically non-Hodgkin' s B cell type.The lesions were solitary in 5 cases and multiple in 2 cases. On MRI, the lesions were long T₁and long T₂ signal, and the tumors showed markedly enhanced without cystic degeneration and ring-like enhancement after contrast injection, and there were mild to moderate peritumoral edema and space occupying effect . Conclusion 　Locations of primary CNS lymphoma vary in brain, adn there are no characteristic MR findings in them. But the lesion displays solid homogeneous enhancement af ter cont rast injection.The final diagnosis depends on immunohistochemistry.