The　influence　of　segments　heat　source　and　mesh　size　on　calculation　accuracy　and　efficiency　of　3-D　EFA　of　multi-pass　butt-welded　pipe　were　investigated.　The　methods　can　meet　the　demand　of　calculation　accuracy　and　high　efficiency　of　3D　finite　element　simulation　of　large　pipes.　The　results　show　that　the　mesh　size　below　or　equals　to　3.3　mm　can　meet　the　accuracy　requirement,　the　segment　heat　source,　which　has　little　efficiencies　on　calculation　accuracy,　can　improve　the　calculations　efficiency　greatly.