Selective Laser Melting (SLM) is an additive manufacturing technology that builds layer-by-layer through a laser-scanned powder bed. The AlSi10Mg alloy formed by SLM has a high density and can ensure the overall quality of the structure. In this paper, the relationship between laser power, scanning speed, scanning distance, and the quality of SLM was determined through FLOW3D numerical simulation. The microstructure and mechanical properties were analyzed under the optimal process parameters. The results showed that the linear energy density will increase with the increase of laser power, resulting in a gradual increase in the width of the single-channel molten pool, so the forming quality increases. With the increase of scanning speed and scanning distance, the density of SLM molding decreases. Under the optimal process parameters, it is found that the internal microstructure distribution of the SLM-formed AlSi10Mg sample is uneven, and there are fine-grained, coarse-grained, and heat-affected zones. The ultimate tensile strength at room temperature can reach 219 MPa, the yield strength can reach 153 MPa, and the impact energy can reach 5.8 J. The surface hardness of XOY plane and XOZ plane are (130±5) HV and (120±5) HV, respectively. Through experimental comparison, it can be found that the mechanical properties of the SLM-formed AlSi10Mg sample are much larger than that of ZAlSi9Mg, which is close to the extruded 6061 aluminum alloy and can meet the application requirements of rapid additive manufacturing.