Based on the ability of catching the change of energy distribution in frequency band for changing in the structure condition by the wavelet packet ana lysis method, the wavelet packet energy accumulated variation index was proposed to detect the structural damage. The damage index was applied to the damage rec ognitions in a continuous twospan girder bridge model in the lab. The results o f measuring acceleration time history from three different kinds of excitation w ays, including vehicle excitation, environment excitation and hammer excitation, indicate that the amount of input energy has the influence on the value of wave let packet energy accumulated variation index. Uniting more than one damage iden tification index results is possible to distinguish the different structural dam age conditions.