Objective To analyze the characteristics and diagnostic value of conventional magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI) and imaging in primary central nervous system lymphoma (PCNSL). Methods The clinical data of 19 patients with PCNSL admitted to our hospital from January 2015 to October -2017 were retrospectively reviewed. The routine MRI, enhanced MRI, FLAIR, DWI, 1H-MRS and PWI scan were performed to analyze the scanned images. Results 35 lesions were found in 19 cases, of which 14 cases were single, 5 cases were multiple, mainly located in the deep brain white matter in the paraventricular area. The lesions were all T1 or slightly low signal, T2 or slightly high signal. The peritumoral edema was light and moderate. The real parts of the 35 lesions were slightly high signal or high signal, and the signal of ADC was lower than that of the contralateral normal parenchyma. 26 lesions were low perfusion, 9 lesions were equal perfusion, the time signal curve had a slow enhancement, and gradually reached the peak. 1 H-MRS spectroscopy showed that the NAA (N-acetyl aspartate) peak decreased, Cr (creatine) peak decreased slightly, Cho (choline) peak increased, and the abnormal tall and broad Lip (lipid) peak appeared, and another 4 lesions appeared inverted Lac (lactic acid) peak. Conclusion Routine and functional magnetic resonance imaging can provide more abundant information for lesion analysis and disease diagnosis of PCNSL patients, and help to improve the accuracy of diagnosis.