Abstract: 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.