Abstract: AlSi10Mg alloy samples were prepared by selective laser melting technology (SLM) under different laser energy densities.The microstructure, forming defects and mechanical properties of the SLM formed alloy were analyzed.The results show that the molten pool of AlSi10Mg alloy sample is irregular elliptical in scanning direction, and the structure in the forming direction is irregular fish scaly and stacked with each other.With the increase of the laser energy density, the porosity of the formed alloy decreases, and the compactness increases, and the tensile propeties are better.When the laser energy density is 54 J/mm³, the tensile strength and elongation of SLM formed alloy are 418.9 MPa and 20.5% respectively.The tensile fracture morphology shows the mixed fracture characteristics of brittleness and toughness under different laser enegy densities.