As　we　know,　the　oxide　film　on　the　surface　of　Al-Li　alloys　has　to　be　cleaned　before　welding　in　order　to　achieve　welds　without　pores.　However,　doing　so　is　difficult　and　may　result　in　undesirable　pollution　with　chemical　cleaning.　In　this　study　as　a　precondition　of　laser　welding　the　plate　of　Al-Li　alloy　was　not　treated　in　any　way　before　welding.　A　CO2　laser　system　was　employed　in　the　study　on　porosity　control　of　1420　Al-　Li　alloy　by　dual-beam　laser　welding.　The　experimental　results　show　that　the　influence　on　the　right　surface　oxide　film　to　the　porosity　in　the　weld　is　bigger　than　that　from　the　backside　when　the　laser　welding　is　in　the　form　of　a　beam　on　the　surface　of　the　plate.　However,　the　sensibility　of　porosity　from　the　backside　oxide　film　has　a　distinct　connection　with　the　formation　of　an　inverse　weld　when　butt-joint　laser　welding　is　carried　out.　Optimized　laser　welding　techniques　have　been　achieved　from　experiments　in　order　to　decrease　the　porosity　in　the　weld　and　increase　weld　quality.　The　tensile　strength　of　the　laser　welding　joint　was　also　tested　in　the　experiment.　The　data　indicate　that　the　average　value　of　tensile　strength　about　the　joints　can　be　up　to　336.1　MPa,　which　is　equal　to　87.5%　of　the　value　of　the　substrate　alloy.