Abstract: To hasten the application of digital radiographic method, computer-aided inspection technique was studied. The image subtracting method was designed appropriately, and then method to extract defects in images from digital radiographic testing was established. After image segmentation with certain threshold and label of individual objects in the image, the defect parameters were calculated, and then defect recognition was done. According to the procedures required by certain radiographic testing standard, the testing result was graded by the parameters and category of defects as calculated above. As a result of above process, software to analyze radiography images and to grade the testing result was developed. With the aid of software, the defects can be quantified; the testing result can be graded to certain level by different testing standards. The work is helpful to promote the application of digital radiographic method.