Objective:To analysis the expression of CD7 in NK/T-cell lymphoma as well as study the correlations between CD7 and clinical survival and prognosis.Methods:The clinical and pathological indicators of 112 NKTCL patients who were admitted to or consulted at the First Affiliated Hospital of Zhengzhou University between May 2008 and December 2019 were analyzed retrospectively. The CD7 expression in the tumor tissues was detected using immunohistochemistry staining, and the influence of CD7 expression on the survival and prognosis in the patients was analyzed.Results:The CD7 expression rate was 84.82% in 112 NKTCL patients, and its expression was not influenced by sex, age, and the primary site. An analysis of the complete clinical data of 72 patients showed that the CD7 expression was significantly correlated with the PINK score, tumor metastasis, and peripheral blood EBV-DNA level. However, the Ann Arbor stage, bone marrow involvement, B symptoms, IPI/aaIPI score, Ki-67, EBER, TIA-1, Granzyme B, LDH, and β 2-MG were not associated with the CD7 expression. The 1-year, 3-year, and 5-year overall survival (OS) rates of the 72 patients were 81.2%, 61.8%, and 58.8%, respectively, and the progression-free survival (PFS) rates were 53.5%, 29.4%, and 24.0%, respectively. The median overall survival (median-OS, mOS) was 81 mon, and the median progression-free survival (median-PFS, mPFS) was 14 mon. The 3-year OS rates in the CD7-positive group and the CD7-negative group were 58.1% and 83.9%, respectively, ( P>0.05) . The 3-year PFS rates were 21.7% and 51.9%, respectively ( P<0.05) . The univariate analysis showed that age, primary tumor site, Ann Arbor stage, IPI/aaIPI score, PINK score, LDH, β 2-microglobulin, EBV-DNA, Ki-67, and CD7 influenced patient prognosis. The multivariate analysis showed that Ann Arbor stage and CD7 were independent prognostic factors for PFS, while PINK score and Ki-67 were independent prognostic factors for OS. Conclusions:The expression rate of CD7 in NKTCL was high and was closely related to poor patient prognosis. The patients with high levels of EBV-DNA, metastatic disease, or high PINK score were more likely to express CD7.