Abstract: To judge and analyze qualitatively the defect of surface and subsurface, through the deep study of NDT to the surface defect of roll, we get the measurement technology of surface acoustic wave on surface defect. Used in practice, it can locate the defect rapidly and accurately. It effectively solve the difficult problem of surface defect on the high-speed steel roll made by new material and surface fatigue cracks on backup roll. It plays a very important promotional part on practice application.