This paper presents a primary study for a method of measurement using PZT sensors which is widely used for SHM. PZT sensor has many advantages when using smart material. It is easy to be shaped to various forms and can be embedded on the materials more conveniently. The development for a practical and quantitative technique for assessment of the structural health condition by PZT sensor associated with wave propagation is investigated. Two aluminum specimens bonded with PZT sensors tested for estimating characteristics of the wave propagate on specimens change by various damage condition cf. line crack, bolt loosening. To estimate condition of the specimens numerically, we suggest impedance and guided wave method in this paper.