Deforming　a　cracked　magnetoelastic　body　in　a　magnetic　field　induces　a　perturbed　magnetic　field　around　the　crack.　The　quantitative　relationship　between　this　perturbed　field　and　the　stress　around　the　crack　is　crucial　in　developing　a　new　generation　of　magnetism-based　nondestructive　testing　technologies.　In　this　paper,　an　analytical　expression　of　the　perturbed　magnetic　field　induced　by　structural　deformation　of　an　infinite　ferromagnetic　elastic　plate　containing　a　centered　crack　in　a　weak　external　magnetic　field　is　obtained　by　using　the　linearized　magnetoelastic　theory　and　Fourier　transform　methods.　The　main　finding　is　that　the　perturbed　magnetic　field　intensity　is　proportional　to　the　applied　tensile　stress,　and　is　dominated　by　the　displacement　gradient　on　the　boundary　of　the　magnetoelastic　solid.　The　tangential　component　of　the　perturbed　magnetic-field　intensity　near　the　crack　exhibits　an　antisymmetric　distribution　along　the　crack　that　reverses　its　direction　sharply　across　its　two　faces,　while　the　normal　component　shows　a　symmetric　distribution　along　the　crack　with　singular　points　at　the　crack　tips.