Abstract: Aiming at the problem of quantitative evaluation of disbonding in adhesive bonding structures, the -3 dB method based on Lamb waves was discussed. The experiments were carried out on steel/rubber adhesive bonding structures with circular disbonding. The results showed that the amplitude of Lamb wave in disbonding area was higher than that in bond area, and the disbonding in the sample could be quantitatively estimated effectively by the -3 dB method.