To　achieve　active　health　monitoring　of　plate-like　objects,　piezoelectric　ceramic　wafers　bonded　in　the　structures　are　applied　for　excitation　and　reception　of　guided　wave　modes　and　proper　modes　are　optimized　for　identification　and　evaluation　of　the　defects.　According　to　the　theoretical　prediction,　compared　with　A0　mode,　S0　mode　in　a　low　frequency　range　with　dominant　in-plane　displacement　and　low　dispersion　is　suitable　for　defect　detection　in　the　aluminum　plate.　The　piezoelectric　ceramic　wafers　11　mm　in　diameter　and　0.4　mm　in　thickness　are　used　for　excitation　and　reception　of　S0　mode　at　300　kHz,　which　is　suitable　for　defect　detection　in　aluminum　plates　with　a　thickness　of　1　mm.　Based　on　the　experimental　results,　an　artificial　hole-like　defect　is　machined　in　the　plate　for　verifying　the　ability　of　defect　detection　using　S0　mode,　and　the　effect　of　the　defect　diameter　on　the　amplitudes　of　received　guided　wave　signals　is　further　analyzed.　Experimental　results　show　that　Lamb　wave　modes　can　be　applied　for　defect　detection　in　the　aluminum　plate　using　the　pitch-catch　method　and　defect　characterization　can　be　achieved　based　on　the　amplitudes　of　the　received　echoes.