Abstract: X-ray DR (digital radiography) imaging is used to detect the lap joint of gas tungsten arc welding for aluminum alloy, the digital reference images of typical welding defects are obtained, and the characteristics of welding defect images are qualitatively analyzed. The statistical analysis of the occurrence frequency of the typical defects was performed and the results showed that the occurrence of cracks, pores and inclusions in TIG welding was high. The defect grades of individual pore or inclusion defect are classified. The crack defects of DR image are enhanced by Laplace sharpening, emboss effect and multi-scale contrast enhancement method, which improved the human visual effect.