A　new　type　of　Al-Zn-Mg-Cu　alloy　sheets　with　T6　temper　were　welded　by　laser　beam　welding　(LBW).　Microstructure　characteristics　and　mechanical　properties　of　the　joints　were　evaluated.　Results　show　that　grains　in　the　heat　affected　zone　(HAZ)　exhibit　an　elongated　shape　which　is　almost　same　as　the　base　metal　(BM).　A　non-dendritic　equiaxed　grain　zone　(EQZ)　appears　along　the　fusion　line　in　the　fusion　zone　(FZ),　and　grains　here　do　not　appear　to　nucleate　epitaxially　from　the　HAZ　substrate.　The　FZ　is　mainly　made　up　of　dendritic　equiaxed　grains　whose　boundaries　are　decorated　with　continuous　particles,　identified　as　the　T　(AlZnMgCu)　phase.　Obvious　softening　occurs　in　FZ　and　HAZ,　which,　mainly　due　to　the　changes　of　nanometric　precipitates.　The　precipitates　in　BM　are　mainly　eta＇,　while　plenty　of　GPI　zones　exist　in　FZ　and　HAZ　adjacent　to　FZ,　in　the　HAZ　farther　away　from　FZ,　eta　phase　appears.　The　minimum　microhardness　of　the　joint　is　always　obtained　in　FZ　at　different　times　after　welding.　The　ultimate　tensile　strength　of　the　joint　is　471.1　MPa　which　is　69.7%　of　that　of　the　BM.　Samples　of　the　tensile　tests　always　fracture　at　the　FZ.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.