Radiation pneumonitis is a common and severe complication of radiotherapy for lung cancer with complex pathogenesis involving inflammation oxidative stress and fibrosis. In recent years molecular biomarkers have made significant advances in the early diagnosis risk prediction and therapeutic evaluation of radiation pneumonitis. Studies have found that inflammatory factors such as transforming growth factor-β1 TGF-β1 interleukin-6 IL-6 and acute-phase proteins like serum amyloid A SAA play crucial roles in the early inflammatory response of radiation pneumonitis. Meanwhile extracellular matrix proteins such as tenascin C TNC and chemokines like CCL18 are mainly involved in the fibrotic phase of lung damage indicating their potential value in late- stage injury. Additionally immune - related factors including C - reactive protein CRP and the CD4 + / CD8 + ratio are considered reflective of systemic inflammation and immune dysfunction in radiation-induced lung injury. Although these biomarkers show promise for the early diagnosis and prognosis of radiation pneumonitis their specificity and sensitivity require further validation through large-scale clinical studies. This review systematically summarizes the current progress in radiation pneumonitis-associated molecular biomarkers analyzes their clinical significance and limitations and explores future research directions such as integrating multi-omics technologies and developing personalized risk prediction models to provide new insights into the precision management and targeted treatment of radiation pneumonitis.