In　this　paper,　a　heat　transfer　model　of　the　filler　wire　in　twin-body　plasma　arc　welding　(TPAW)　was　established.　The　total　power　transferred　to　the　filler　wire　included　anode　effect　power,　resistance　power　and　plasma　arc　power.　The　influences　of　the　wire　current,　wire　extension　and　plasma　gas　flow　rate　on　the　power　transferred　to　the　filler　wire　were　studied　using　the　location　of　the　molten　region　of　the　filler　wire　as　the　characteristic　parameter.　The　studies　showed　that　the　anode　effect　power　caused　by　the　increase　in　wire　current　can　increase　the　total　power　transferred　to　the　filler　wire　by　50　%　or　more　while　the　current　flowing　through　the　tungsten　electrode　of　the　plasma　torch　remains　constant.　This　is　confirmed　by　analyzing　the　weld　shape　under　different　wire　currents.　The　resistive　heating　of　the　wire　excision　is　not　a　major　component　of　the　total　power　transferred　to　the　filler　wire,　and　the　wire　extension　can　be　set　to　a　reasonably　wide　range　of　values.　There　was　a　threshold　value　for　the　influence　of　the　plasma　gas　flow　rate　on　plasma　arc　power.　When　the　plasma　gas　flow　rate　was　greater　than　the　threshold　value,　plasma　arc　power　remained　nearly　constant　as　the　plasma　gas　flow　rate　increased.　Therefore,　the　total　power　transferred　to　filler　wire　in　TPAW　was　composed　of　anode　effect　power　and　plasma　arc　power.　©　2021　The　Society　of　Manufacturing　Engineers