Abstract: Digital radiography method was used to detect welded joints of aluminum alloy with different thickness. The process parameters such as voltage, current, exposure time and magnification were optimized to make the detection sensitivity meet the standard requirements. On this basis, digital radiography and film radiography were respectively carried out on fusion weld and friction stir welded joint of aluminum alloy to obtain the typical defect images. The morphology distribution, size and properties of the defects were compared and analyzed. The defect detection ability of digital radiography was analyzed and the reliability of digital radiography detection results was verified. The result showed that the detection sensitivity of digital radiography was superior to the standard requirements. Meanwhile, the defect detection capability of digital radiography was basically the same as that of film radiography, and the dimension error was less than 5%.