An　in　process　distortion　mitigation　method,　localized　thermal　tensioning　technique,　also　named　DC-LSND　welding　technique,　has　been　developed　by　introducing　a　trailing　heat　sink　during　conventional　GTAW.　The　thermal　elasto-plastic　finite　element　analysis　procedure　was　developed　to　quantitatively　study　the　effect　of　heat　sink　on　the　thermomechanical　process　during　welding　and　to　find　out　the　stress　and　distortion　controlling　mechanism　of　the　proposed　technique.　Welding　trials　were　also　conducted　to　verify　the　effectiveness　of　the　technique　and　the　validity　of　the　finite　element　model.　Finally,　effects　on　controlling　results　of　process　parameters　were　studied　for　heat　sink;　i.e.,　the　distance　between　heat　sink　and　welding　arc　(d)　and　cooling　intensity　of　heat　sink　(h).　Based　on　these　studies,　the　methods　to　determine　optimal　heat　sink　parameters　are　presented　for　engineering　applications.