Tensile　and　fatigue　properties　of　Al-Mg-Mn-Zr-Er　alloy　and　its　laser　welded　joints　were　investigated,　and　the　corresponded　S-N　curves　and　conditional　fatigue　limits　were　obtained.　The　microstructure　and　fatigue　fracture　were　observed　to　explore　the　main　causes　of　fatigue　failure　of　Al-Mg-Mn-Zr-Er　alloy　laser　welded　joint.　The　results　show　that　the　microstructure　of　the　joint　was　inhomogeneous.　The　base　metal　consisted　of　typical　rolled　structures,　but　the　fusion　zone　mainly　comprised　small　equiaxed　grains　with　a　size　of　40　μm,　and　the　heat-affected　zone　was　recrystallized　microstructure.　The　tensile　strength　of　the　welded　joints　was　lower　than　that　of　base　metal,　and　the　joint　strength　coefficient　was　0.73.　The　conditional　fatigue　limits　of　the　welded　joint　was　68.5%　of　that　of　the　base　metal,　and　the　main　influence　of　fatigue　performance　were　the　microstructure　inhomogeneity　in　the　joint　and　the　second　phase　inclusions　in　the　weld.