Radiotherapy can cause functional and morphological changes in the brain tissues of patients with primary or metastatic malignant brain tumors, leading to radiation-induced brain injury. However, the pathogenesis of radiation-induced brain injury has not yet been unanimously determined, and its research advances and treatment protocols are yet to be elucidated and improved. In this study, we explore the pathogenesis of radiation-induced brain injury from the perspective of vascular injury, inflammatory reactions, neuronal dysfunction, glial cell injury, and gut microbiota and reviewed the advances in research on its treatment and prevention. The purpose is to provide a reference and theoretical basis for the research and clinical diagnosis and treatment of radiation-induced brain injury.