Abstract: To test the tube-to-tubesheet fillet weld internal defects, the paper proposed the ray digital detection method which was based on the linear array detector. This paper introduced the imaging principle of the linear array detector, and analyzed the image characteristics of the linear array detector of both X and γ-ray irradiation by the radiography test of the tube-to-tubesheet fillet weld specimens. The test showed that compared to the X-ray, γ-ray collected images quality was lower, and overall gray was darker, acquisition time was longer. Some of the key factors were obtained that affected the γ-ray linear array detector digital image quality. At the same time this paper provided an experimental and application basis for which the linear array detector was used in γ-ray test.