Abstract: Under certain working conditions, it is impossible to place the ultrasonic transducer on the bottom surface of the rod-shaped component to complete the defect inspection, such as the parallel steel wires of the bridge and the inserted steel bar in the grouting sleeve in prefabricated building. In order to improve the applicability of ultrasonic guided wave technology, a method of length detection and defect localization is proposed by using a 50 kHz drycoupled ultrasonic shear wave transducer. Combining theoretical analysis, simulation and experimental verification,the results show that the optimal excitation angle of the transducer is 90°, that is, the excitation direction is perpendicular to the axis of steel wire; the relative errors of both simulated and experimental results are less than 2%for steel wires with different lengths and different defect locations.