Abstract: In the practice of radio-graphic inspection engineering, the atypical defect images are usually found in the pipeline installation stage of nuclear power plant, which increases the difficulty of the quality evaluation and control of the pipeline weld. Combined with the imaging characteristics and defect formation mechanism of pipeline radiographic inspection, the atypical defect images of weld radiographic inspection of pressure pipelines in nuclear power plants can be roughly divided into wall thickness thinning, misalignment of welding, weld forming defects, base metal defects, foreign body defects, pit defects, surface mechanical damage, etc. Through the classification of atypical displays and the identification, evaluation and processing of relevant negative images, a comprehensive method for the inspection and evaluation of pipeline welds in nuclear power plants was proposed, which provided a certain reference for the welding quality control of similar pipeline engineering construction.