The invention relates to the technical field of intelligent manufacturing, and discloses a rare earth erbium element reinforced AlSi7Mg aluminum alloy powder specially used for SLM (selective laser melting), and a preparation method and an application thereof. The rare earth erbium element reinforced AlSi7Mg aluminum alloy powder specially used for SLM comprises, by mass, 5.5-8.5% of Si, 0.55-0.75% of Mg, 0.2-0.9% of Er, 0.05-0.5% of Zr, below 0.1% of Zn, below 0.1% of Cu, below 0.1% of Mn, below 0.1% of Fe, below 0.05% of Ni, below 0.05% of Pb, below 0.05% of Sn, below 0.07% of Be, below 0.10% of O, and the balance of Al. AlSi7Mg aluminum alloy powder is reinforced with the rare earth erbium element, so the strength of an SLM molded part is improved, the weight reduction of an aviation part is realized, and the full performance of the SLM technology in the aerospace field is promoted.