Although much effort has been devoted to explore the behavior of the composite lattice truss core sandwich structures, little research has been undertaken into non-destructive evaluation (NDE) and health control of this new structure. This article presents the development of a baseline-free NDE method to determine the debonding of truss bar in composite lattice truss core sandwich structures. The method is proposed based on the uniform load surface (ULS) curvature, and developed according to the synergy of gapped smoothing method (GSM) and Teager energy operator (TEO), which is denoted as GSM-TEO method. The effects of local damage on the vibration characteristics of different composite lattice truss core sandwich structures are firstly investigated, and then, experiment and numerical simulation are conducted to assess the performance of the proposed method. It is demonstrated that the GSM-TEO method is reliable and applicable for damage localization in composite lattice truss core sandwich structures.