To　solve　the　problem　of　calculating　the　1000　kV　AC　extra-high　voltage　transmission　line　3-D　electromagnetic　problem,　based　on　the　finite　element　analysis　method,　the　calculation　model　of　1000　kV　AC　extra-high　voltage　transmision　line　is　proposed.　According　to　the　simplified　straight　conductor　model　and　the　actual　line　model　with　sag,　calculations　of　3-D　electromagnetic　field　of　transmision　line　were　made　respectively.　The　calculation　results　show　that　the　transverse　distribution　trends　of　electric　field　are　consistent　under　the　straight　line　model　and　the　wire　with　sag　on　the　same　height.　On　the　same　height,　the　electric　field　straights　are　consistent　along　the　longitudinal　of　line.　The　maximum　value　of　the　longitudinal　electric　field　strength　of　sag　line　is　in　the　lowest　sag　part.　At　the　same　time　the　value　of　electric　field　strength　decreases　gradually　along　the　longitudinal　of　the　sag　line.　The　calculated　result　and　the　measured　value　are　close.　The　results　of　magnetic　field　strength　and　electric　field　strength　have　similar　rules.　The　accurate　results　of　electromagnetic　strength　of　transmission　line　can　be　obtained　by　3-D　electromagnetic　field　modeling.　The　calculation　method　of　the　3-D　electromagnetic　field　model　considering　sag　has　a　certain　reference　value　for　the　electromagnetic　research　of　EHV　transmission　line.