In　this　paper.　the　basic　principle　of　Optical　Voltage　Transformer　(OVT)　based　on　Pockels　effect　is　introduced.　A　comparison　is　made　between　transverse　Pockels　effect　and　longitudinal　Pockels　effect.　And　OVT　is　unable　to　present　the　distribution　of　internal　field　directly.　Therefore,　it　is　necessary　to　simulate　its　electric　filed,　and　the　accuracy　of　the　simulation　results　is　important　for　OVT＇s　design.　For　the　axisymmetric　model,　in　order　to　improve　the　efficiency　of　calculation　a　three-dimensional　(3D)　structure　is　usually　simplified　as　a　two-dimensional　(2D)　model.　To　compare　and　analyze　the　differences　between　the　calculated　results　obtained　by　using　OVT＇s　voltage　sensor　head　with　2D　and　3D　models,　different　shapes　of　EGO　crystal　in　voltage　sensor　head　are　constructed　respectively,　and　the　finite　element　simulation　software　Ansoft　Maxwell　is　used.　The　simulation　results　indicate　that　the　maximum　electric　field　intensity　is　quite　different　between　2D　and　3D　models　of　sensor　head.　And　in　the　3D　simulation,　different　shapes　of　BGO　crystal　have　different　maximum　electric　field　intensity　of　the　sensor　head.　Compared　with　2D　simulation,　3D　simulation　is　more　real.　So　in　an　actual　operation　situation,　it　should　analyze　the　OVT　with　3D　model.