AlSi10Mg alloy displays excellent properties, such as good air tightness, good fluidity, small thermal cracking tendency, small shrinkage and high strength. It is widely used in automotive, aerospace and other fields. With the increasing demand for lightweight components, the structure and shape of aluminum alloy parts become more complex, and traditional casting techniques is difficult to meet market demands. In view of this, the rapid solidification of AlSi10Mg alloy by selective laser melting (SLM) was studied. The AlSi10Mg alloy was prepared by selective laser melting (SLM) technique. The microstructure, phase composition and mechanical properties of the alloy after laser treatment and melting at different temperatures were analyzed. The experimental results show that the microstructure of the AlSi10Mg alloy by selective laser melting consists of the matrix region and the heat-affected zone. The molten pool between the different layers are elliptically superposition. The width of the molten pool is about 250～300 μm, and the depth is about 100～200 μm. After the aging treatment, due to the diffusion of Si atoms, the eutectic silicon in the dendritic state is completely transformed into a granular shape, and as the aging temperature increases, the average size of the eutectic silicon increases. The phase of the alloy consist of Al matrix phase and Si phase before and after the aging treatment. However, after aging, the peak of the Al phase shifts to the left due to precipitation of Si atoms in the supersaturated Al(Si) solid solution. After the selective laser melting, the alloy has the highest hardness value, and the hardness value decreases sharply after the aging temperature. When the temperature rises at any time, the hardness value decreases. Selective laser melting technology can effectively refine the microstructure of AlSi10Mg alloy and significantly improve the mechanical properties of the alloy.