Welding　of　1420　aluminum-lithium　alloy　has　been　investigated　using　a　high　power　YAG　Laser.　The　results　show　that　the　threshold　for　penetration　welding　of　1420　Al-Li　alloy　is　about　1.2　×　106　W/cm2,　lower　than　those　of　the　traditional　Al　alloys.　Pores,　which　are　the　main　welding　defects,　mainly　locate　near　the　bond　line.　Tensile　test　shows　that　the　weld　near　the　bond　line　is　the　weakest　part　of　the　joint.