Magnetostrictive　transducer　for　the　use　of　defect　detection　in　stainless　steel　helical　bellows　has　been　developed.　The　finite　element　models　of　magnetic　field　distribution　law　have　been　calculated　using　commercial　package　Comsol　Multiphysics　firstly　and　the　results　confirm　that　magnetic　field　intensity　can　be　increased　observably　after　setting　the　ferromagnetic　material.　An　artificial　defect　of　circumferential　crack　has　been　identified　by　the　improved　transducer　with　wrapping　nickel　alloys.　The　uncertainty　synthesis　formula　has　been　derived　and　standard　uncertainty　of　measurement　result　has　been　calculated.　The　results　have　been　providing　a　theoretical　basis　for　nondestructive　evaluation　in　stainless　steel　helical　bellows　using　magnetostrictive　transducer.