Abstract Carbon fibre reinforced polymer (CFRP) is an excellent material used to strengthen concrete structures, but its debonding failure is one of the main reasons restricting the wide application of this technique. Although there are several studies concerning the debonding detection of CFRP-strengthened concrete structures, this issue still remains unresolved. In this paper, a piezoelectric ceramic (PZT) was used to detect the damage of the CFRP-concrete interface via the wave-based method. First, different damage types were prepared in a concrete column, and PZT detection was used to study the damage. The wave signal was filtered and analysed based on the evaluation model. The damage type and thickness were detected, which verified the reliability of the detection method. Then, a debonding process of CFRP-strengthened concrete beam under bending loading was monitored by PZT detection. The wave-based method can show the clear process of damage development, which confirmed the feasibility of the technique for on-site application.