Abstract: Abstract Geometric parameters is an important factor affecting the quality of the radiographic image, the current domestic and foreign standards for digital radiographic inspection of pipeline ring weld transmittance geometry are directly referenced to the film photographic method standards, there are large errors. In this paper, based on the requirements of the RCC-M specification and the theory of geometrical unsharpness, we studied the difference between the film photographic method and the DR technology in the test arrangements, discussed the control of the geometric parameters of DR technology of nuclear-grade pipeline welds, established the geometrical unsharpness-Geometric parameters model, and formulated the number of times of transmittance of digital radiographic transmittance of pipeline circumferential weld.