Objective To explore the pathological manifestation and CT、MR findings of primary central nervous system lymphoma (PCNSL). Methods 18 cases'CT、MRI and pathological datas confirmed with PCNSL were retrospectively analyzed. Results ① There were 18 cases with 26 lesions, and 6 lesions located at the basal ganglia, 5 lesions at corpus callosum, 5 lesions at thalamus, 6 lesions at periventricular deep white matter, 4 lesions at cerebral hemisphere shallow. 14 cases showed nodular mass, 4 cases of butterfly-shaped. 6 cases with edema, 12 cases with mild edema. ② CT scan: 6 cases showed slightly higher density, 2 cases showed equal density; enhanced scan showed significantly enhanced. ③ MR scan: T1WI 14 cases showed slightly lower signal and 4 cases showed equal signals on T1WI; T2WI 14 cases showed slightly higher signal and 4 cases showed equal signals on T2WI, all showed high or slightly higher signal on DWI. Enhanced scan: all significantly enhanced, including 4 cases with peripheral enhancement more visible with "ring sign", 4 cases showed "butterfly-like", 6 cases showed "fist sign", 2 cases showed "sharp sign", 2 cases were round. 8 cases with 1H-MRS examination, NAA peak reduced of varying degrees, Cho peak significantly increased, 7 cases with Lip peak increased significantly, 4 cases with Lac peak. Conclusion CT and MRI findings of PCNSL had certain characteristics, comprehensive analyzed the CT and MRI features could make correct diagnosis.