A modified model combining electro-mechanical impedance (EMI) technique and reverberation matrix method (RMM) is presented to quantitatively correlate crack parameters with piezoelectric signatures through the proper dynamic analysis of a smart cracked beam. The structural members of cracked beams are modeled as Timoshenko beams for flexural motion as well as the cracks are treated as massless rotational springs. For a structural member with surface-bonded PZT wafers, a coupled structural system is considered. Then, an analytical expression of impedance involving information of cracks is derived. Based on this model, comparison study is implemented with self-conducted experiment and existent research results. Finally，the effect of some physical parameters including crack information on EMI signatures is also investigated for structural health monitoring.