Abstract: According to the invalidity of the sink roll shaft hand of one CGL, the same material shaft hand with simulated crack was designed and produced. Through comparing the experiments with different probes and by different methods, the miniwal size of the crack on shaft head inside angle R was confirmed by convention ultrasonic testing method. Experimentation proved vertical wave inspection was better than transverse wave inspection to the crack on shaft head inside angle R; Using probe B2S(E), there was higher inspection sensitivity to the crack which was not critically extended, but it was difficult to find exactly and determinate the initial crack under 1 mm depth.