Abstract: Purpose:To Analysis the CT representations of radiation-induced pulmonary injury,evaluate its CT diagnosis value. Material and Method: The data of 160 patients with radiation induced pulmonary injury were collected, and reviewed to their CT findings, and compared CT features with X-ray's. Result: In 160 patients of first examination, and compared CT features with X-ray's. Result: In 160 patients of first examination, 66 patients represent acute radiation-induced pneumonia, 40 cases are in transition, stage, and 54 cases are in fibrosis stage. CT findings: radiation -induced pneumonia stage represents symmetrical high-density image or only pass-through grade light reduce in irradiation area, transition stage represents strip lard small patch image in irradiation area, and scar stage represents thick strip and patch image in the area, and bound shrink. The appearing time of acute radiation-induced pneumonia in CT is earlier than in plain film. And CT is even more easy and precision than plain film to show the focus in secrete part, distinguish apiece stage and differentiate pulmonary injury from original lesion(or recrudescence).Conclusion: CT can definitely show the radiological features and presumedly by-stages of radiation induced pulmonary injury, and has much higher sensitivity than plain film, and has preferable guidance and differentiation function in clinic.