Magnetic　field　distribution　of　optical　current　transducer　(OCT)　is　affected　by　temperature,　so　it＇s　necessary　to　establish　the　electromagnetic-thermal　coupled　simulation　model.　Based　on　the　analysis　of　thermal　effects　on　hysteresis　loop　and　air　gap　length,　a　three　dimensional　finite　element　method　model　of　OCT　with　magnetic　concentrator　was　built.　After　several　iterative　solution　process　such　as　electromagnetic　field-thermal　field-hysteresis　loop-air　gap　length,　the　electromagnetic-thermal　coupled　simulation　when　measuring　direct　current　was　achieved.　The　relationship　between　temperature　rise,　magnetic　field　intensity,　environment　temperature　and　current　was　determined.　A　new　design　of　air　gapped　amorphous　core　with　stable　temperature　characteristics　was　proposed　based　on　simulation　results.　Experimental　results　show　that　the　electromagnetic-thermal　coupled　simulation　method　and　the　design　with　stable　temperature　characteristics　are　useful.