The effects of welding wire with and without Er on the forming, microstructure and tensile properties of the 2524 aluminum alloy in the state of de-oxide-film and de-coated-aluminum-layer were investigated by laser butt welding. The results showed that, there is an aluminum clad layer with a thickness of about 30 μm on the surface of the 2524 aluminum alloy, and there is an oxide film with a thickness of about 4 μm on the surface of aluminum clad layer; under the same surface state, the weld width of the welding wire with Er is larger than that of the welding wire without Er, the forming coefficient is less than that of the welding wire without Er, the average spacing (Ed) of equiaxed dendrites and the average spacing (Cd) of columnar dendrites in the weld center and near the fusion line of the welding wire with Er are less than that of the welding wire without Er, and the width of the maximum solute poor zone near the grain boundary of the fusion zone is less than that of the welding wire without Er; In the state of de-oxide-film and de-coated-aluminum-layer, the fractures of the samples with and without Er are located in the fusion zone of the welded joint, the tensile strength and elongation of the samples with Er are higher than those without Er, and the strength and plasticity of the samples with de-coated-aluminum-layer state are better under the same welding wire conditions. This is mainly related to the existence of micron primary Al3Er phase which can refine grains, and nano Al3Er phase which can strengthen in welding wire with Er.