Effects　of　laser　modification　welding　(LMW)　on　formation　of　full-penetration　weld　were　studied,　which　were　based　on　the　laser　beam　welding　(LBW)　process　of　5A02　aluminum　alloy.　The　results　indicated　that　the　welding　defects　(such　as　undercut,　surface　depression　and　so　on)　could　be　improved　obviously,　and　the　microstructure　of　joint　by　LMW　could　be　finer　than　that　of　joint　only　by　LBW.　Besides,　the　strength　and　toughness　of　joint　would　also　be　increased　to　some　extent　by　LMW　after　full-penetration　LBW.　Therefore,　the　LMW　is　an　effective　method　in　order　to　strengthen　joint　of　LBW.