Abstract: Transforming growth factor beta 1 (TGF-β1) is an important fibrogenic cytokine, and its expression level can reflect the severity of pulmonary fibrosis. Radiation-induced lung injury (RILI) includes early radiation-induced pneumonia (RP) and late radiation-induced pulmonary fibrosis (RIPF). The development of RP to RIPF is accompanied by the increase of the expression level of TGF-β1. Understanding and mastering the molecular mechanism of TGF-β1 in the occurrence and development of RP and RIPF is of great significance for the prevention and treatment of RILI. This paper reviews the fibrogenic effect of TGF-β1 in the process of RILI and its mechanism.