Abstract: This paper analyzes the differences between digital radiography and conventional X-ray films in terms of technical indicators and measurement methods, points out their differences in image evaluation, introduces the digital radiographic evaluation of the various image processing methods and shortcomings of evaluation function. It also puts forward the "gray curve section" auxiliary qualitative and new ideas like monofilament accurate measurement and defect quality indicator self height measurement, and provides beneficial enlightenment for the popularization and application of digital X-ray.