Selective laser melting(SLM) technology is adopted to form AlSi10Mg alloy and the microstructure and tensile property at room temperature are studied. The results show that SLM formed AlSi10Mg alloy has fine microstructure and high room temperature tensile properties, and the microstructure and strength show obvious anisotropy. The high cooling rate in SLM process refine the previous α-Al dendrites significantly, and the different solidification conditions in the core and boundary of melt pool can not only lead to different scales of α-Al dendrites, but determine the growth morphology of α-Al dendrites, which follows the law of epitaxial growth. Combination of the morphology and evolution of Al-Si eutectic structure of sample in different orientations, the anisotropy of microstructure is investigated. Furthermore, the strength of tensile samples along deposition (L) and scanning (T) directions is almost the same, while the elongation shows double relationship, so the different mechanical properties are due to its anisotropy of ductility. The SEM morphology of tensile fracture presents the crack mechanism, the size of the dimple, morphology of Al-Si eutectic structure and formation of micro cracks prove that the crack mode is intergranular fracture. The experimental results show that the microstructure and properties of SLM formed AiSi10Mg are higher than those of conventional cast components, which make SLM technology realizable in engineering application of typical components manufacturing in the field of aero engine control system.