Stereotactic biopsy can provide enough tissue for clear pathological diagnosis with less damage, which is better than conventional craniotomy. At present, the better treatment mode for this disease is: stereotactic biopsy to clarify the pathology, combined chemotherapy regimen containing HD-MTX with intrathecal chemotherapy is preferred, and whole brain radiotherapy can be considered after chemotherapy for patients under 60 years of age. Primary CNS lymphoma has good chemotherapeutic efficacy, with a median survival time of 5 years after chemotherapy; patients under 60 years of age have a better outcome, with 74% of patients surviving for more than 10 years. Prior to the application of HD-MTX, the treatment model for this disease was radiotherapy followed by chemotherapy, and the standard first-line regimen for systemic NHL, the CHOP regimen (CTX+ADM+VCR+Pred), was used, which was not applicable to primary CNS lymphoma, and the addition of chemotherapy with the CHOP regimen after radiotherapy did not prolong survival compared with radiotherapy alone, and was more toxic and difficult to be tolerated by elderly patients. Combination chemotherapy regimens containing HD-MTX (>3g/m2) or even single-agent HD-MTX can significantly prolong survival; Ara-C is the second most effective drug after MTX; other drugs that can easily penetrate the blood-brain barrier, such as VM-26 and Topotecan, are also commonly used in first- or second-line treatment regimens. Since radiotherapy can accelerate the recovery of blood-brain barrier function, stimulate vascular endothelial cell proliferation and induce drug resistance in tumor cells, thus affecting the efficacy of chemotherapy, and the administration of HD-MTX after radiotherapy can significantly increase the incidence of cerebral white matter lesions, radiotherapy is administered after HD-MTX chemotherapy.