Abstract: Objective:To study the related factors of severe acute radiation-induced lung injury (SAR) caused by IMRT and concurrent chemotherapy for non-small cell lung cancer. Methods:We retrospectively analyzed the data of2 323 non-small cell lung cancer pa-tients who underwent IMRT radiotherapy and concurrent chemotherapy at the Department of Radiotherapy of Tianjin Medical Univer -sity Cancer Institute and Hospital from January2010to January 2014. We analyzed the clinical factors and parameters that affect dose by univariate and multivariate analysis.Results: A total of 2 323 patients enrolled and 1 241 cases suffering from acute radiation- in-duced lung injury with the rate of 53. 4%. Only185 cases suffered from SARP with a rate of7. 96%. Univariate analysis showed that the gender, histopathological type, total radiation dose, V 5 (%), and average dose rate are not related to SARP (P>0. 05). By contrast an age of > 60years, 1% predicted FEV, docetaxel + carboplatin/cisplatin chemotherapy, V20(%), V 30(%), and mean lung dose (MLD) are sig -nificantly related to SARP ( P<0. 05). Multivariate analysis showed that a patient age of > 60years, docetaxel + carboplatin/cisplatin che -motherapy, V20(%), and V30(%) are the independent risk factors of SARP. Conclusion: Among the non-small cell lung cancer patients undergoing IMRT radiotherapy and concurrent chemotherapy, further attention should be given to elderly patients, patients receiving docetaxel and platinum chemotherapy, as well as V20and V30with high doses. The necessary preventive treatment should be given to reduce the incidence of SARP, improve the quality of life of patients, and reduce the incidence of respiratory failure and mortality.