Abstract: Based on the rigid bolt and soft bolt use prone to crack defects in the parts of the analysis, according to the structure characteristics, probes the characteristics of bolt, bolt in shear wave oblique probe and longitudinal wave probe method for ultrasonic flaw detection, detection of threaded reflected wave to adjust the shear wave flaw detection sensitivity, as well as defects, deformation wave of recognition method, as the key to effectively detect the crack defects.