Abstract: 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.