Abstract: Using Moiré Pattern technology, a three-dimensional welding seam image sensing system was introduced. A pair of gratings with a small angle, a CCD camera and other optical parts made this system.Three-dimensional information of a welding seam was obtained by the relationship between its shape and the offsets of deformed Moiré lines to the top surface of the welding seam, which were decided by the optical structure in the system. The realization method and its image processing were explained.Three-dimensional welding seam images were obtained with experiments. Initial experimental results shows that the Moiré Pattern three-dimensional measurement technology is simple and successful for the three-dimensional image of the edge and shape of a welding seam.It can be used to accurately identify and pick-up characteristics of welding seam more.