Abstract: Objective To evaluate dose volume history in process of lung cancer radiotherapy using image fusion technique completely.Methods 25 patients who did not undergo operations, median age 54 and Karnofsky Performance Status≥70.All received three-dimensional conformal radiation therapy using CT-sim, and were scanned by CT-sim repeatedly after 40-50Gy radiotherapy.We made image fusion of the images before and after radiotherapy using ACQsim working station and overlayed total dose of normal tissues through radiotherapy planning system.Results Radiotherapy was finished for every patient and total dose was 60-66Gy.DVH could reflect the suffering dose of normal pulmonary tissue, spinal cord and heart completely.Conclusion Adjustment of total dose during radiotherapy period by the suffering dose of normal tissues could decrease complication occurrence in process of radiotherapy.