Objective To study the CT and MRI features of primary brain lymphoma, then help to better diagnose. Methods From 2005 March to 2013 June, 20 patients with primary lymphoma were selected to retrospectively analyzed of the MRI and CT imaging features of patients. Results In these patients, 15 cases with single lesion and 5 cases multiple. The whole brain position were made. 18 cases of supratentorial, and 2 cases of infratentorial . The mean lesion was (2.6 × 2.5 × 2.3) cm. On CT tomography images, the lesion was round, like round, clear boundary, size was generally 2 cm in diameter, had better resolution. In CT images, patients with intracranial mass scan for the density or high density, in 20 patients examined, 14 cases of high density mass. The 20 patients were enhanced scanning, 18 cases of all 20 cases was strengthened, uniform and enhanced obviously; 2 cases of annular enhancement; On MRI lesions, it showed clear boundary, homogeneous signal, TIWI for low signal, T2WI is slightly high signal or signal enhancement, uniform, including inhomogeneous enhancement in 2 cases and 2 cases of dural tail sign. Pathological results of 20 cases were B cell non Hodgkin's lymphoma (NHL). Conclusion CT and MRI in the diagnosis of primary brain lymphoma can play a certain role, but the diagnosis is difficult, or to rely on pathological examination.