Abstract: OBJECTIVE To explore the relationship between EB virus（EBV） infection and prognosis of patients with extranodal nasal-type natural killer（NK）/T cell lymphoma. METHODS A total of 120 patients with extranodal nasal-type NK/T cell lymphoma who were treated in the Fifth Affiliated Hospital of Zhongshan University from Aug 2013 to Oct 2016 were enrolled in the study. The copy number of EBV-DNA in peripheral venous blood was detected by real time fluorescent quantitative reverse transcription-polymerase chain reaction（qRT-PCR）. The enrolled patients were divided into the EBV-positive group and the EBV-negative group. According to presence or absence of anti-EBV treatment, the patients of the EBV-positive group were divided into the anti-EBV treatment group and the non-anti-EBV treatment group. The clinicopathological features, curative effect and prognosis were compared between the two groups of the patients. The influencing factors for the prognosis were observed. RESULTS Ann Arbor staging was later in the EBV-positive group than in the EBV-negative group; the proportion of middle to high risk prognostic index NK（PINK） was greater, and the proportion of lactic dehydrogenase（LDH） with no less than 240 U/L was significantly greater（P＜0.05）. The objective response rate of the EBV-positive group was 44.68%, significantly lower than that of the EBV-negative group（P＜0.05）. The objective response rate of the anti-EBV treatment group was 83.33%, significantly higher than that of the non-anti-EBV treatment group（P＜0.05）. The follow-up that lasted till Oct 31, 2019 showed that 77 of 120 patients survived, and 43（35.83%） died due to illness. The 2-year and 3-year overall survival（OS） rates and progression free survival（PFS） rates were significantly lower in the EBV-positive group than in the EBV-negative group（P＜0.05）. The EBV tested positive before the treatment was an independent prognostic risk factor for 3-year PFS and OS（P＜0.05）. CONCLUSION The EBV infection may reduce the clinical curative effect of the patients with extranodal nasal-type NK/T cell lymphoma, which is closely related to their clinicopathological features and prognosis.