Abstract: This study focused on coated pipelines and employed digital detector array (DDA) technology to perform grayscale analysis of radiographic imaging for pressure pipelines with coatings. Using the first-order derivative grayscale method, the inner and outer walls of the pipeline were segmented and extracted, and then the measurement of wall thickness in coated pressure pipelines was realized. The wall thickness measurement positions of the DDA were verified using ultrasonic thickness measurement, and the results from both methods were basically consistent. The proposed method had certain application value.