Abstract: DR imaging technology was used widely in modern industry for its many advantages. For large workpiece testing, due to the size restrictions of imaging plate, an image mosaic software was required to illustrate the whole radiographic testing image of the workpiece. When radiographic testing was carried out with a multi freedom degree system, an image mosaic problem was taken on the horizontal and vertical direction of the image. Testing on-site found that, the turntable moving direction on horizontal was no any effect to the switching image quality, but the vertical moving of turntable would lead to poor quality of image stitching. The analyzing results showed that it was caused by the magnification difference on the vertical direction. Therefore, in order to achieve an effective large-scale workpiece testing, the radiographic testing system should be designed with panel detector moving in horizontal and vertical direction, and not being the turntable movement.