Abstract: This paper introduces a new method for field determination of a new type of heat-resistant steel materials (such as P91 steel) shear wave sound velocity using normal probes. Using the variant transverse wave from the normal probe in the workpiece, exploring the causes and the propagation path of the variant shear wave , deduced the transverse wave sound velocity calculation formula for the material. When testing, correct the angle of refraction and AVG curve.So that increasing the positioning accuracy of the defects ,and avoiding the undetected and misjudgment.