The　Er-containing　Al-Mg　alloy　was　welded　by　laser　beam　welding.　Microstructures　and　mechanical　properties　of　the　joints　were　analyzed,　and　the　effects　of　erbium　on　the　microstructure　and　properties　of　the　weld　and　the　heat　affected　zone　were　investigated.　The　results　show　that　due　to　the　addition　of　rare　earth　element　Er,　the　grain　size　of　the　weld　center　reduces　to　about　30　mu　m;　a　＂fine　grain　layer＂　appears　near　the　fusion　line;　no　significant　grain　growth　occur　in　the　heat-affected　zone;　the　micro-hardness　in　the　cross　section　distributes　in　W-shape.　The　effect　of　Er　on　the　tensile　strength　of　welded　joints　is　not　obvious,　and　the　tensile　strength　is　70%　of　that　of　the　base　material.