To explore the clinical characteristics, diagnosis, treatment outcome and prognosis of de novo CD5 positive diffuse large B cell lymphoma (CD5(+)DLBCL), clinical data of 10 patients with pathologically confirmed CD5(+)DLBCL were retrospectively analyzed. The results indicated that 9 out of 10 patients were older than 60 years. All cases were in III/IV stages according to Ann-Arbor Staging System. Bone marrow biopsy with immunohistochemistry showed lymphoma involvement in 5 cases. Nine patients received chemotherapy with anti-CD20 monoclonal antibody (Rituximab) except one. Five cases achieved CR, two cases achieved PR, two cases achieved SD, one case achieved PD. Eight cases died within 2 years because of relapse or disease progression, in which 3 cases developed central nervous system lymphoma. The median survival time was 16 (1-23) months, 2-year survival rate was 20.40%. It is concluded that de novo CD5(+) DLBCL is rare in clinic, but it is a kind of highly aggressive lymphoma with poor prognosis. So, new treatment strategy should be explored.