Digital radiographs of long large objects such as water pipelines, show radiation images which have poor contrast and low signal to noise ratio, especially in the strongly attenuated areas. The examination of the whole objects will spend much time. So, how to shorten the examination time and improve the contrast and signal to noise ratio of radiation images, is the essential problems. The images reconstructed by only a few projective images in digital Tomosynthesis, have a sensible improvement of signal to noise ratio and contrast, compared with digital radiographic images. This will be helpful to the nondestructive testing of the large objects, Therefore, the application of digital Tomosynthesis to the CT nondestructive testing of large objects will effectively improve the Examination efficiency and image quality. Firstly employ digital Tomosynthesis to obtain the axial images of large objects, for the sake of locating the suspicious defects. After indicating the ROIs of defects, radial images will be reconstructed by CT reconstruction methods. Thus the 3D regions of the defects will be rapidly located by the integration of digital Tomosynthesis and CT.