In this study, Al-Mg-Sc-Zr aluminum alloy was prepared by selective laser melting (SLM). The effects of different processing parameters on the formation and different aging conditions on mechanical properties of SLM-formed samples were investigated. The results show that the high density samples can be obtained at a high laser power and a low laser scanning speed. The layer by layer stacking of the molten pool can be observed along the deposition direction of the sample. The nanoparticles are observed at both the inside and boundary of molten pool. After aging treatment at different temperatures, the hardness and compressive yield strength of the sample first increase and then decrease. The maximum yield strength ~469 ± 4 MPa is achieved after aged the sample at 400 ° C for 3 h.