Abstract: In order to improve the strength of the laser selective melted (SLM) Al-Si-Mg aluminum alloy, a Cu-modified Al-Si-Mg-Zr alloy with high Mg content is fabricated. The processability, microstructure, and mechanical property of the SLM-fabricated Al-Si-Mg-Zr-Cu alloy are systematically studied. The results indicate that the sample exhibits good SLM processability at low laser power (250 W), with a maximum relative density of 99.8%. The microstructure of the alloy is mainly composed of equiaxed grains, with a small amount of columnar grains distributed in the melt pool. The grains contain reticular substructures, and there are nanoscale precipitates exising in the α-Al matrix. When the luse power is 250 W, and the scanning speed is 1 200 mm/s, the microhardness, tensile strength, yield strength, and elongation of the samples are (158 ± 4)HV, (461 ± 25) MPa, (397±32) MPa, and (2.4±0.7)%, respectively. The strength of the SLM-fabricated Al-Si-Mg-Zr-Cu alloy is higher than that of the SLM-fabricated Al-Si-Mg alloy.