As　a　precondition　of　laser　welding,　the　plate　of　Al-Li　alloy　wasn＇t　treated　before　welding.　A　DC035　CW　CO2　laser,　in　the　TEM00　mode,　with　output　up　to　3500　W,　was　employed　to　experimentally　study　the　porosity　control　of　1420　Al-Li　alloy　by　dual-beam　laser　welding.　The　experimental　results　show　that　the　influence　from　the　surface　oxide　film　on　the　porosity　in　weld　is　deeper　than　that　from　the　backside　one　when　the　laser　welding　is　in　the　form　of　beam　on　the　surface　of　plate.　However,　welding　porosity　has　a　distinct　connection　with　the　sensibility　of　backside　oxide　film　and　the　backside　formation　in　the　weld　when　the　butt　joint　laser　welding　is　carried　out.　The　optimized　laser　welding　techniques　were　achieved　experimentally　to　decrease　the　porosity　in　weld　and　increase　the　weld　qualities.　The　tensile　strength　of　welded　joints　of　butt　joint　laser　welding　was　experimentally　tested　too.　The　data　indicate　that　the　average　tensile　strength　of　the　joints　could　reach　up　to　336.1　MPa,　which　is　equal　to　87.5%　of　the　substrate　alloy.