Abstract: The working principle of the shear wave probe is analyzed. In the automatic calibration work principle foundation, the use of the velocity known synchronizes with the unknown, to realize the automatic calibration of sound velocity and zero off-set. Using the test block CSK-ⅠA tests the automatic calibration of the probe index point and angle of refraction. A new method calculates the probe frontier to reduce the error. At last, the paper analyzes the influence factors of defect evaluation.