Laser　butt　welding　was　carried　out　for　the　joining　of　5A06　aluminum　alloy　sheet　by　using　6　KW　fiber　laser.　The　effect　of　welding　speed　on　the　surface　morphology,　microstructure,　micro-hardness,　tensile　strength　and　porosity　were　studied　by　means　of　optical　microscopy　(OM),　a　scanning　electron　microscope　(SEM),　an　energy　dispersive　spectrometer　(EDS),　a　Vickers　hardness　tester　and　a　universal　mechanical　tensile　test.　The　results　show　that　the　weld　macro　morphology　tends　to　be　smooth　and　the　surface　defects　are　reduced　with　an　increase　in　welding　speed.　The　heat-affected　zone　was　very　small　due　to　the　large　cooling　rate.　The　columnar　dendrites　grow　from　the　fusion　line　along　the　direction　of　the　temperature　gradient.　The　microstructure　of　the　weld　zone　was　in　the　form　of　equiaxed　grains.　The　micro-hardness　of　the　weld　was　lower　than　that　of　the　base　material.　The　micro-hardness　and　the　tensile　strength　were　gradually　increased　with　an　increase　in　welding　speed.　When　the　welding　speed　is　12　mm　x　s(-1),　the　micro-hardness　and　the　tensile　strength　were　increased　to　96.5　%　and　56.2　%　of　the　base　mental,　respectively.　The　porosity　ratio　decreased　at　first,　and　then　increased　with　the　increase　in　welding　speed.　The　lowest　porosity　ratio　was　1.99　%　when　the　welding　speed　was　12　mm　x　s(-1).　In　summary,　the　quality　of　the　weld　was　better　when　the　welding　speed　was　12　mm　x　s(-1).