This thesis mainly introduces the research and application of digital radiography（DR） and industrial computed tomography（industrial CT） technology on parts for railway freight wagons by the X-RAY source of 9 MeV electron linear accelerator. Using DR and industrial CT technology to test frame brace welding,wheel and cylinder block,not only realize high efficient and accurate testing evaluation of inner defects of parts,but also achieve the size measurement of defect and structure. In addition,the defects of shape and position are clear and intuitive to display by two-dimensional or three-dimensional images,and obtains the basic data of the process analysis and evaluation,which provides a scientific and effective detection for improving the manufacture quality and process stability,analyzing,improving and optimizing the process method.