In　this　paper,　a　non-destructive　testing　(NDT)　method　based　on　highly　non-linear　solitary　waves　(HNSWs)　was　employed　to　detect　defects　in　the　metal　plate　of　an　adhesive　composite　metal　structure.　Firstly,　HNSWs　were　generated　by　applying　impulses　to　a　one-dimensional　granular　chain　of　steel　spheres.　Proof-of-concept　finite　element　(FE)　simulations　were　then　performed　using　Abaqus　software　to　investigate　the　reflection　behaviour　of　HNSWs　at　the　interface　of　the　chain　and　the　two-layer　material　with　defects.　The　time-of-flight　(　TOF)　of　primary　reflected　solitary　waves　(PSWs)　was　confirmed　as　a　good　indicator　for　defect　localisation　and　sizing.　A　HNSW　generator　and　detector　device　was　used　in　the　experiment　and　HNSW　B-scan　and　C-scan　inspections　of　adhesive　composite　steel　specimens　were　achieved.　The　TOF　imaging　results　accurately　indicated　the　locations　of　cylindrical　defects　in　the　bottom　steel　block.　The　linear　correlation　between　the　peak　value　of　the　pulsed　TOF　profile　and　the　defect　diameter　was　determined.　The　contours　of　TOF　with　different　values　were　introduced　to　reconstruct　the　shape　of　the　circular　defective　region.　Through　selecting　the　correct　threshold　of　TOF,　the　relative　error　of　the　area　surrounded　by　the　contour　compared　to　the　actual　area　of　the　five　investigated　defects　could　be　less　than　6.5%.