The　spectrums　of　laser-induced　plasma　in　CO2　laser　welding　of　6061　aluminum　alloy　are　measured　through　PI　Pro2500i　transient　spectrometer.　Boltzmann　diagrams　can　be　used　to　calculate　the　average　temperature　of　laser-induced　plasma,　which　are　deduced　from　Mg　I　spectrums　between　200-600　nm.　The　influence　of　welding　parameters,　such　as　laser　power,　welding　speed,　focus　position　and　shielding　gas,　on　laser-induced　plasma　temperature　are　investigated　separately　and　the　reasons　are　also　discussed.　Under　the　experimental　conditions,　laser　power　plays　little　role　on　laser-induced　plasma　temperature　(6000　K)　when　it　exceeds　the　threshold　power　of　laser　penetration　welding.　The　effect　rule　of　welding　speeds　on　laser-induced　plasma　temperature　likes　inverted　U　curve.　Laser-induced　plasma　temperature　has　been　increased　and　then　decreased　when　the　flow　rate　of　shielding　gas　is　increased　for　a　given　diameter　of　nozzle.　Laser-induced　plasma　temperature　will　increase　500-1000　K　when　adding　argon　in　to　helium.