Abstract: In the installation and construction of engineering process pipeline, the quality of welding joint has an important impact on the reliability of main facilities and supporting facilities, and nondestructive testing is an important means to ensure the welding quality. At present, the traditional radiographic testing technology is mainly used to detect the small diameter pipe, which has the disadvantages of long detection cycle and low efficiency, thus affecting the progress of the project. The cold cathode digital X-ray imaging detection technology is developed for small diameter tubes. The detection sensitivity and resolution of the technology are analyzed. The detection rate and quantitative error of the technology are analyzed by comparing with the traditional X-ray detection technology. The results show that the cold cathode digital X-ray imaging testing technology can meet the detection requirements of small diameter tubes, and has broad application prospects.