To　address　the　challenge　of　ultrasonic　detection　of　multiple　defects　in　large-scale　tank　bottom　plates,　a　multichannel　magnetostrictive　sensor　was　designed　and　developed　to　effectively　excite　SH　(Shear　Horizontal)　mode　guided　waves.　The　optimal　overall　scheme　of　the　sensor　was　obtained　by　considering　the　sensor　excitation　energy,　coupling　efficiency,　and　fabrication　process.　Through　experimental　tests,　the　consistency　of　each　channel　of　the　sensor　is　evaluated,　and　the　center　frequency　and　detection　range　of　the　sensor　are　measured.　To　detect　defects　of　varying　sizes　and　depths　in　steel　plates,　a　rotating　total　focus　imaging　method　is　proposed.　And　we　conducted　experiments　using　a　multi-channel　magnetostrictive　sensor　to　achieve　SH0　guided　wave　imaging　of　multiple　defects　across　the　full　domain.　Our　experimental　results　demonstrate　that,　across　8　rotations,　we　achieved　a　minimum　relative　position　error　of　4.32%　and　a　minimum　absolute　angle　error　of　2.16　degrees.　Our　research　provides　an　effective　solution　for　ultrasonic　detection　of　tank　bottom　plates,　and　the　proposed　method　is　also　applicable　for　defect　detection　in　other　large　plate-like　structures.