Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) is the most common subtype of peripheral T-cell lymphoma. The overall incidence rate of this disease is low and the heterogeneity is strong. At present, its diagnosis mainly relies on exclusive diagnosis. Clinically, the first-line treatment of PTCL-NOS mostly refers to CHOP-like chemotherapy regimens for B-cell non-Hodgkin lymphoma, but its efficacy is unsatisfactory, with high recurrence rate and poor long-term survival. The widespread application of new targeted drugs and antibody conjugated drugs, such as chidamide, pralatrexate and brentuximab vedotin have improved the therapeutic effects of patients to some extent. However, the prognosis of relapsed/refractory patients is still not satisfactory. This article reviews the pathological characteristics, immunophenotype, genetic characteristics, clinical features, and treatment progress of PTCL-NOS.