Abstract: The AlSi10Mg alloy was prepared by selective laser melting (SLM). The microstructure of the as-deposited alloy was analyzed, and effects of three heat treatment processes (T6, T2, T6+T2) on the morphology and distribution of eutectic silicon were studied. The results show that the molten pool on surface of the as-deposited alloy was divided into three areas, fine grain zone, coarse grain zone and remelting zone, in order from center to border. The eutectic siliton was in the form of short fiber with nanometer size. Before and after heat treatment, the AlSi10Mg alloy consisted of aluminum, silicon and Mg₂Si phases. The eutectic silicon distributed more uniformly after heat treatment, showing that the homogeneity of the structure was improved. The silicon content of eutectic silicon of the as-deposited alloy increased after heat-treatment by T6 and T2 processes in turn, and the purity of eutectic silicon was improved.