Objective To study the clinical and pathological characteristics, as well as diagnosis, treatment methods and prognosis of adult patients with chronic active Epstein-Barr virus infection (CAEBVI). Methods Clinical and pathological data of 8 adult patients with CAEBVI admitted to a hospital in Gansu Province from January 2017 to December 2022 were collected retrospectively, clinical and histopathological characteristics, EBV-related test results, as well as treatment and prognosis of patients were analyzed. Results Among 8 CAEBVI patients, 3 were males and 5 were females, with the median age of 21.5 years. The median time from onset to diagnosis of CAEBVI was 7 months. The main manifestations were fever, pancytopenia (involving two or three peripheral blood lines), as well as lymph node enlargement, hepatomegaly and splenomegaly. The quantifications of plasma EBV nucleic acid (DNA) were all >1.0×10³. The sorting results of EBV infected cells showed that 3 cases were T lymphocytes infection, 2 were NK cell infection, and 3 were co-infection of T lymphocytes and NK cells. Bone marrow cytological examination of 8 patients showed no atypical lymphocytes, while 6 patients showed hemophagocytic cells. Flow cytometey (FCM) typing results showed that no abnormal cell population was detected in all the 8 patients, and no myeloid, B lymphocyte, T lymphocyte and NK cell markers were expressed. The positive rate of T cell receptor (TCR) gene rearrangement was 37.5% (n=3). Histopathology showed that most cases (n=6, 75.0%) expressed CD3, partial cases expressed CD4, CD8, CD56, TIA-1, and EBV encoded RNA (EBER), all were positive. The survival rate of patients after treatment was 50.0% (n=4), the follow-up time was 6-51 months, the 1-year survival rate was 85.7%, and the median survival time was 24 months. Conclusion CAEBVI is characterized by variable clinical manifestations that may lead to fatal complications. Early diagnosis and individualized treatment should be performed to reduce mortality of patients.