The　characteristics　of　temperature　field　have　been　studied　numerically　and　experimentally　for　a　titanium　alloy　sheet　when　welded　with　an　improved　gas　tungsten　arc　welding　method,　in　which　a　trailing　spot　heat　sink　is　introduced　to　control　the　welding　stress　and　distortion.　The　impinging　jet　model　is　employed　to　describe　the　intense　heat　transfer　between　the　cooling　media　and　the　top　surface　of　the　workpiece.　By　comparing　this　improved　technique　to　the　conventional　gas　tungsten　arc　welding　(GTAW)　process,　the　influence　of　the　spot　heat　sink　is　investigated.　Results　show　that　a　low　temperature　region　exists　where　the　heat　sink　is　applied;　a　saddle　backed　temperature　field,　with　the　lowest　temperature　at　the　centre　and　higher　temperatures　at　both　sides,　is　formed　during　the　improved　welding　method;　and　the　time　that　the　metal　spends　at　high　temperature　is　shortened　in　the　improved　welding　process.　Experimental　measurements　of　the　thermal　histories　compare　well　with　the　calculations,　which　prove　the　validity　of　the　finite　element　model　and　the　impinging　jet　heat　transfer　model　in　simulating　the　gas　tungsten　arc　welding　process　with　a　trailing　heat　sink.　(C)　2004　Elsevier　B.V.　All　rights　reserved.