The　Lamb　wave　testing　for　the　automobile　spot　weld　is　proposed,　which　can　be　used　for　evaluating　the　diameter　and　the　maximum　tension　load　of　the　spot　weld.　The　propagation　mechanics　of　Lamb　wave　in　the　sample　of　spot　weld　is　difficult　to　be　investigated　by　analytical　method　because　of　the　wave　dispersion　and　type　transformation　in　the　wave　conductor　with　complex　shape,　so　the　finite　element　method　is　adopted　to　simulate　the　Lamb　wave　propagation　in　the　samples.　The　simulation　results　reveal　that　the　A0　modal　Lamb　wave　transmitted　through　the　weld　nugget　has　a　close　relationship　with　the　characters　of　nugget　shape　such　as　the　nugget　diameter　and　the　indentation　depth.　Thus,　the　shape　and　mechanical　property　of　spot　weld　may　be　evaluated　by　Lamb　wave　method.　A0　modal　Lamb　wave　can　be　excited　by　adjusting　the　incident　angle　of　probe.　Experimental　results　indicate　that　the　peak　value　of　received　A0　modal　Lamb　wave　decreases　with　the　increase　of　the　nugget　diameter　and　the　maximum　tension　load　of　the　spot　weld,　which　are　consistent　with　the　finite　element　modulation,　and　can　be　used　in　the　nondestructive　evaluation　on　practical　spot-welded　structure.　©　2011　Journal　of　Mechanical　Engineering.