Abstract: In order to accurately measure the image width of micro weld tested by radiographic testing, an edge detecting method of laser-targeted double-border synchronization tracking was put forward by combining the characteristics of weld image and equipment and by using both hardware and software combination. Through cutting through the image, expansion and identifying the start point, the accurate weld edge information was got, providing a basis for the accurate measurement of the weld width. The actual image processing results proved the effectiveness of the methods.