The interdigital transducer (IDT), developed from surface acoustic wave devices, has been gradually applied to structural health monitoring systems due to its operating frequency, adjustable frequency bandwidth and low loss. Therefore, it has a wide application prospect in smart materials and structures. In this paper, the wideband trapezoidal interdigital transducer (TIDT) is studied for the shortage, narrow bandwidth, of the existing rectangular IDT. The finite element analysis method was used to optimize the TIDT structure, and the TIDT performance was tested. The preliminary application of TIDT for structural damage detection was studied through experiments. The experimental results show that TIDT improves damage recognition accuracy in practical applications and has broad application prospects.