The　laser　ultrasonic　technology　has　the　advantages　of　non-contact　and　high　inspection　efficiency.　It　has　been　widely　concerned　in　the　field　of　nondestructive　testing.　Fully　utilizing　the　characteristic　of　high　spatial　resolution　of　the　laser　ultrasound　technology,　a　defect　detection　method　for　plate　structures　was　put　forward　by　the　combined　use　of　the　compact　rectangular　array　and　laser-based　Lamb　wave　technology.　The　continuous　wavelet　transform　was　used　to　process　the　wide-band　Lamb　wave　signal　with　low　time-domain　resolution　so　as　to　obtain　a　narrow-band　signal　with　high　time-domain　resolution　at　a　given　frequency.　The　linear　mapping　compensation　technology　was　used　to　eliminate　the　dispersion　in　the　narrow-band　signal.　The　obtained　signals　after　dispersion　compensation　were　used　for　defect　imaging.　The　dispersion　compensated　signals　were　processed　by　integrating　the　amplitude　imaging　technique　and　the　sign　coherence　factor　imaging　technique,　and　then　the　defect　imaging　and　location　for　an　aluminum　plate　were　achieved.　Based　on　this,　the　effects　of　element　spacing　and　number　on　the　beam　steering　and　the　quality　of　defect　imaging　of　the　compact　rectangular　array　were　analyzed.　When　the　number　of　array　elements　is　16　and　the　array　element　spacing　is　one　wavelength　of　Lamb　wave　mode,　the　width　of　the　main　lobe　is　narrow　and　there　are　no　grating　lobes,　the　defect　imaging　quality　is　improved　effectively.　©　2020,　Editorial　Office　of　Journal　of　Vibration　and　Shock.　All　right　reserved.