Aluminum alloy is an excellent lightweight metal material with low density, high specific strength, and good corrosion resistance. In order to improve the mechanical properties of aluminum alloy fabricated by laser selective melting (SLM), this paper proposed a strengthening method of aluminum alloy material in which Cu element was used as simple particle, and explored the influence of the proportion of Cu element on the forming quality and properties of aluminum alloy fabricated by SLM. The results showed that the doping of Cu powder can refine the microstructure grain of aluminum alloy simply and effectively, and improved the tensile strength of aluminum alloy material. Al₂Cu phase could effectively refine the grain and form a more compact micro equiaxed crystal structure in the overlapping area. With the increase of the content of copper powder, the Al₂Cu phase generated in the structure gradually increased, and the grain size gradually decreased from 3.30 μm to 2.12 μm. The microstructure was refined. The sample containing 5% copper powder had the highest tensile strength of 460 MPa, which was 20.4% higher than that without copper powder. However, after excessive copper powder was dopped, the performance of the sample was reduced to a certain extent due to the presence of un-melted particles. This study is of great significance to further improve the mechanical properties of aluminum alloy fabricated by SLM.