Objective To analyze the value of conventional magnetic resonance imaging (MRI) and 3D multi-planar reconstruction and enhancement in the diagnosis of primary central nervous system lymphoma (PCNSL). Methods Fifty-seven patients with PCNSL confirmed by pathology during the period from April 2014 to April 2018 were examined by conventional MRI before surgery, and MRI conventional enhanced scan was also performed. Among them, 35 cases underwent 3D multi-planar reconstruction and enhanced imaging. The general MRI findings, the signal intensity, enhancement morphology and enhancement sign on T1WI and T2WI were observed. Results A total of 79 lesions were detected in 57 patients with PCNSL, mostly in the supratentorial brain parenchyma, followed by the subcolumn. Most of them were round, nodular or patchy infiltrative lesions with a maximum diameter of 2 to 7.5 cm. MR plain scan showed that most lesions were homogeneous, with equal or slightly lower signal on T1WI, slightly higher or equal signal on T2WI, high signal on DWI and an ADC value of (0.75±0.15)×10-3mm2 /s. Compared with the ADC value of normal white matter in the contra lateral hemisphere (0.91±0.19)×10-3mm2 /s, there was significantly different (P<0.05). The conventional enhanced scan found that most lesions showed clumpy, nodular, flaky and ring-like enhancement or mild to moderate enhancement, and a few lesions showed necrosis and cystic lesion. The effect of 3D enhanced reconstruction after enhancement is significantly better than that of conventional enhanced scan in displaying the "Horseshoe sign", "Soft meningeal enhancement sign", "Ependymal enhancement sign", "Vessel encapsulation sign in the lesion", "Vessel encapsulation sign beside the lesion" and "Butterfly sign" of the lesion(P<0.05). Conclusion The conventional MRI findings of PCNSL, such as lesion location, size and signal intensity are characteristic. The 3D multiplanar reconstruction and enhancement can enrich the enhancement information which can be used as a diagnostic basis for PCNSL to improve the diagnostic rate.