Abstract: Due to the different materials of each layer of the laminated structure, there are many factors that will affect the bonding quality between the layers, and under the action of external forces in manufacturing, use and maintenance, local separation, debonding, spalling and other damage between the coating and the matrix material often occur. These damages can weaken the mechanical properties of the laminated structure, and the accumulation over time may lead to failure or damage, reduce the service life of the structure and even cause safety accidents. Therefore, it is very necessary to carry out damage detection research on laminated structures. The object of research in this paper was the bonded laminate structure of aluminum plate and rubber plate. When the physical properties of the material (such as density, Poisson´s ratio, Young´s modulus, etc.) were unknown, the amplitude nonlinearity of guided wave propagation in the damaged structure was analyzed. By using this amplitude nonlinearity to establish the damage difference coefficient, a baseline-free damage localization algorithm was proposed. Experiments were carried out on preset debonded laminates and the results verified the effectiveness of the method for single damage and multiple damage detection.