Abstract: Real-time automatic X-ray inspection technique has the advantage of good consistency and high automation, so it is fit for on-line inspection of long weld. However this technique is hard to be applied in practice due to high false alarm and missed detection rates. Aiming at this problem, the real-time X-ray automatic inspection system for weld defects in pipe was established. The information fusion was proposed in two defect segmentation methods of weld X-ray image et al, background subtraction and grey level wave analysis, thus the false alarm and missed detection rates were decreased greatly. This system was being used for steel pipe manufacture in the West-East natural gas transmission project.