Abstract: Ultrasonic resonance spectroscopy is a nondestructive method used to test materials by generating free vibrations using ultrasonic excitation. This method can be used to determine the mechanical properties of materials. In this article, finite element simulation technology was used to study the impact of structural defects on the ultrasonic resonance spectrum and natural frequency. The results showed that the resonance frequency obtained from the ultrasonic resonance spectrum can determine the location and size of structural defects. In addition, the ultrasonic resonance spectra of test blocks with and without defects were obtained through experimental research. By comparing the two spectra, it was confirmed that ultrasonic resonance spectroscopy can accurately detect structural defects. Finally, the accuracy of finite element simulation was verified by comparing the results with those obtained from experiments. Through simulation and experimental research, it has been proven that ultrasonic resonance spectroscopy is a valuable non-destructive testing method for detecting structural defects.