Inclusion Criteria:  Age 18-69 years; KPS score ≥ 60 points or ECOG score ≤ 2 points; expected survival time of more than 3 months; PCNSL confirmed pathologically by tissue biopsy (limited to the brain, not accompanied by lymphoma in other parts of the body) , And histopathological type is diffuse large B-cell lymphoma; no chemotherapy contraindications (blood picture and physiological examination result time <7 days); at least one measurable lesion according to RECIST standards; no other serious diseases that conflict with this plan ; Follow-up is possible; other anti-tumor drugs are not used during this treatment period, and bisphosphonate anti-bone metastasis therapy and other symptomatic treatments can be applied; understand the situation of this study and sign the informed consent.  Exclusion Criteria:  Those who are currently receiving other chemical, radiotherapy and targeted therapies (received chemotherapy within 3 weeks, received radiotherapy within 2 weeks, or have not recovered from the acute toxicity of any previous treatment); pregnant or lactating women; yes Any uncontrollable medical disease (including active infection, uncontrolled diabetes, severe heart, liver, kidney dysfunction, and interstitial pneumonia, etc.); those who are contraindicated with chemotherapy such as cachexia; have had other malignant tumors in the past Those who have uncontrolled infections; those who have a history of uncontrollable mental illness; those who are considered unsuitable to participate in this trial by the investigator.