Based　on　the　trial　of　twin-spot　laser　welding　of　2　mm　thick　1420　Al-Li　alloy,　the　effect　of　laser　welding　parameters　including　laser　power,　welding　speed,　defocusing　distance　and　twin-spot　adjust　parameters　including　focus　spacing,　focus　orientation,　intensity　distribution　of　the　foci　on　the　formation　of　the　joints　was　studied.　The　characteristics　of　weld　formation　in　single-spot　and　twin-spot　welding　were　compared　and　analyzed.　The　results　indicated　that　the　process　window　in　twin-spot　laser　welding　was　narrower　than　in　single　spot　laser　welding,　but　the　weld　quality　was　improved　prominently.　The　effect　of　focus　spacing　on　the　weld　formation　was　related　to　intensity　distribution　of　the　foci,　which　had　an　essential　influence　on　the　welding　result.　In　order　to　get　a　higher　penetration　and　failure　free　seams,　a　40%　to　60%　and　a　60%　to　40%　distribution　were　better.　Furthermore　the　focus　orientation　had　another　slight　impact　on　the　welding　result.