ObjectiveTo analyze the clinical and dosimetric impacts on radiation pneumonitis (RP), and provides data for radiotherapy planning. MethodsWe reviewed 59 non-operative esophageal cancer patients who underwent radiotherapy from October 2010 to November 2012 to identify the correlation between the clinical and dosimetric parameters with acute radiation pneumonitis (ARP) and severe acute radiation pneumonitis (SARP) by t-Test, Chi-Square Test and logistic regression analysis. ResultsAmong the 59 patients, 33 (55.9%) developed ARP, in whom 9 (15.3%) developed SARP. Univariate analysis showed that lung infection during radiotherapy, mean lung dose (MLD), and dosimetric parameters are significantly correlated with RP. Multivariate analysis revealed lung infection during radiotherapy, MLD≥13 Gy, and V30≥13% were significantly correlated with the increasing risk RP. ConclusionLung infection during radiotherapy, MLD, and V30 are the influencing factors of RP, which should be seriously considered when formulating radiotherapy plan to avoid RP.