Abstract: In view of the aliasing of ultrasonic echo signal due to the constraints of thickness, number of layers, and types of composite materials, a method for detecting the interface debonding of composite structures was proposed in this paper, which directly used the energy characteristics of the ultrasonic longitudinal wave reflection of the aliasing signal. Firstly, the ultrasonic signal reflection and transmission characteristic model of single- and multi-layer composite structures was established. Then, the ultrasonic echo energy characteristics of structures under different interface bonding states were extracted and analyzed. Based on this model, the debonding detection simulation of steel-rubber-rubber composite structures was carried out. The interface debonding was identified by the introduction of energy difference of signals. Finally, the steel-rubber-rubber composite structural debonding samples were discovered by the ultrasonic flaw detection equipment. Both theoretical analysis and experimental verification show that the proposed method may realize effective defect detection of multi-layer composite structures.