Magnetostriction　is　investigated　to　evaluate　the　stress　relief　caused　by　pulsed　magnetic　field　treatment,　because　this　physical　property　is　closely　associated　with　residual　stress.　Magnetostriction　of　different　stressed　samples　is　measured　in　this　paper.　The　stress　variations　caused　by　pulsed　magnetic　treatment　are　also　compared.　It　is　found　that　magnetostriction　variations　are　closely　associated　with　stress　changes.　Thermodynamic　potential　is　used　to　find　the　relationship　between　them.　Based　on　several　assumptions,　we　find　that　the　product　of　magnetostriction　amplitude　and　stress　magnitude　is　nearly　a　constant　during　magnetic　field　treatment,　which　is　valuable　for　stress　relief　evaluation　and　optimizing　processing　parameters.　This　conclusion　is　testified　by　stress　measurements,　and　the　calculated　values　are　in　accordance　with　the　experiment　results.　©　2011　Higher　Education　Press　and　Springer-Verlag　Berlin　Heidelberg.