Laser-induced　plasma　obtained　during　the　process　of　CO2　laser　welding　aluminum　alloys　have　been　studied.　Laser-induced　plasma　occurs　in　laser　welding　and　reveals　important　information　about　technological　process.　Optical　spectrums　of　laser-induced　plasma　in　CO2　laser　welding　6061　aluminum　alloy　were　measured　through　PI　Acton　Research　Spectra　Pro2500i　transient　spectrometer.　Boltzmann　diagrams　could　be　used　to　calculate　the　average　temperature　of　laser-induced　plasma,　which　were　deduced　from　Mg　I　spectrum　lines　between　200　and　600　nm.　The　influence　of　welding　parameters,　such　as　laser　power,　welding　speed,　focus　position　and　shielding　gas,　on　laser-induced　plasma　temperature　were　investigated　separately　and　the　reasons　were　also　discussed.　Under　the　experimental　conditions,　laser　power　played　little　role　on　laser-induced　plasma　temperature　(6000K)　when　it　exceeded　the　threshold　power　of　laser　penetration　welding.　The　effect　rule　of　welding　speeds　on　laser-induced　plasma　temperature　liked　inverted　U　curve.　Laser-induced　plasma　temperature　had　been　increasing　before　decreasing　when　the　flow　rate　of　shielding　gas　was　increasing　for　a　given　diameter　of　nozzle.　Laser-induced　plasma　temperature　would　increase　from　500　to　1000K　when　adding　Argon　in　Helium.