Objective To investigate prognostic factors in patients with primary central nervous system diffuse large B-cell lymphoma (PCNS-DLCBL).Methods The clinical data of 71 patients with PCNS-DLCBL confirmed by pathology and clinical tests, who were admitted to our hospital from 1991 to 2015, were retrospectively analyzed.All patients received chemotherapy, mainly with high-dose methotrexate (HD-MTX, 66/71), and 59 patients received radiotherapy, mainly with whole brain radiotherapy (WBRT)±local boost.The Kaplan-Meier method was used to calculate survival rates, the log-rank test was used for survival comparison and univariate prognostic analysis, and the Cox model was used for multivariate prognostic analysis.Results Fifty-eight patients achieved a complete response (CR), ten achieved a partial response (PR), and three had progressive disease (PD).The 5-year overall survival (OS) rate was 43%, and the 5-year progression-free survival (PFS) rate was 34%.The univariate analysis showed that the factors associated with OS included the following:age of onset, Karnofsky Performance Scale (KPS) score, single or multiple lesions, whether to receive radiotherapy, evaluation results after radiotherapy and chemotherapy, and the presence or absence of recurrence (P=0.000-0.047);the multivariate analysis showed that the three factors that affected OS were age of onset, KPS score, and the presence or absence of recurrence (P=0.000-0.022).The univariate analysis revealed that chemotherapy regimen, whether to receive radiotherapy, total radiotherapy dose, WBRT dose, evaluation results after radiotherapy and chemotherapy, and the presence or absence of recurrence were the factors associated with PFS (P=0.000-0.028);the multivariate analysis revealed that KPS score and the presence or absence of recurrence were associated with PFS (P=0.000-0.011).Conclusions Among patients with PCNS-DLCBL, younger age, higher KPS score, and no recurrence are associated with better OS, and single lesion, radiotherapy, and better evaluation results after radiotherapy and chemotherapy may be associated with better OS;higher KPS score, better evaluation results after radiotherapy and chemotherapy, and no recurrence are the factors associated with better PFS, and HD-MTX chemotherapy, radiotherapy, higher total radiotherapy dose, and higher WBRT dose may be associated with better PFS.Whether to receive radiotherapy after achieving a CR with chemotherapy and the target area and dose of radiotherapy need to be further studied.