Development　of　magnetism,based　nondestructive　testing　technology　and　the　Microelectronic　mechanical　system　require　accurate　computation　of　perturbed　magnetic　fields　generated　by　mechanical　stress.　In　this　paper　based　on　the　linearized　magnetoelastic　theory,　the　governing　equations　and　continuity　conditions　to　determine　the　perturbed　magnetic　fields　were　formulated　for　the　case　of　weak　external　magnetic　fields　such　as　the　earth＇s　magnetic,field.　Under　those　weak　magnetic　fields,　the　effect　of　the　magnetic　fields　on　mechanical　deformation　was　neglected.　As　a　result,　the　interaction　between　the　deformation　and　the　magnetic　field　was　simplified.　The　effect　of　deformation　on　the　perturbed　magnetic　field　was　taken　into　account　by　introducing　the　displacement　gradient　into　the　boundary　conditions　that　the　perturbed　field　should-satisfy.　As　examples,　analytic　solutions　of　the　perturbed　magnetic　field　of　infinite　plates　with　and　without　a　round　hole,　which　are　subjected　to　tensile　stresses　and　weak　external　magnetic　fields,　were　obtained　by　the　approach　presented.　The　results　show　that　the　perturbed　magnetic　fields　induced　by　stress　are　three　orders　less　in　magnitude　of　intensity　than　that　of　magnetic　fields　without　stress,　and　some　prominent　local　features　such　as　that　has　more　peaks　and　decays　more　rapidly　in　the　radial　direction　than　the,　case　of　stress　free　that　are　predicted　by　the　solutions.