The　mechanisms　of　two　kinds　of　magnetic　field　mainly　distributed　around　power　source　and　cables　are　analyzed,　and　their　accuracy　is　verified　through　measurements.　It＇s　found　that　several　modulation　effects　on　current　from　rectifier　to　inverter　module　in　the　power　source　result　in　stacking　effect　of　magnetic　field　among　power-frequency　magnetic　field　and　magnetic　fields　generated　by　the　rectifier　and　inverter　module.　Furthermore,　the　magnetic　field　frequency　around　the　cables　strongly　depends　on　the　frequency　of　IGBT;　low-frequency　and　time-varying　magnetic　field　strength　increases　as　the　current　ripple　increase,　but　varies　inversely　as　distance　approximately.　Extra　electromagnetic　radiation　to　operator　results　from　closing　to　and　bending　the　cables,　therefore,　it＇s　great　significant　to　further　understand　and　descript　the　electromagnetic　radiation　under　welding　environment　to　standardize　the　welding　criteria　and　also　to　reduce　magnetic　filed　radiation　exposure　as　far　as　possible.