In　this　paper,　an　electromagnetic　acoustic　transducer　(EMAT)　method　using　rotating　bias　magnetic　field　was　proposed　for　NDT　of　delamination　defect　in　a　thin　multilayer　tube　of　W-Cu　monoblock　in　ITER　divertor.　To　investigate　its　feasibility,　a　numerical　simulation　code　was　developed　for　EMAT　signal　simulation　of　tube　configuration　and　uniform　bias　magnetic　field.　The　EMAT　signals　of　a　typical　EMAT　transducer　under　bias　magnetic　field　applied　outside　the　tube　were　simulated　for　deboning　defect　of　different　size　in　the　W-Cu　interface　of　the　mono-block.　The　reasonable　sound　speed　and　simple　dependence　of　the　signal　amplitude　on　defect　size　demonstrated　that　the　developed　code　is　efficient　and　the　proposed　rotating　bias　field　EMAT　is　feasible　for　inspecting　delamination　defect　in　thin　multilayer　tubes.　In　addition,　an　experiment　was　carried　out　to　investigate　the　influence　of　the　rotating　speed　on　the　EMAT　signals.　It　is　found　that　a　normal　rotation　speed　does　not　give　significant　influence　on　the　EMAT　signals,　which　further　support　the　validity　of　the　rotating　bias　field　EMAT.