Abstract: The microstructure, hardness and phase transformation of 7A09 aluminum alloy prepared by selective laser melting (SLM) after solid solution and two-stage aging were investigated by means of OM, microhardness tester, SEM and TEM. The results show that the microstructure of the untreated 7A09 alloy has significant inter-channel heterogeneity. After solution and two-stage aging treatment, the alloy shows uniform and fine microstructure, and the channel structure disappeares. The hardness of the alloy under the treatment is higher than that of the original alloy (82 HV), reaching an average of about 160 HV. The precipitation of S phase (Al₂CuMg) and θ phase (Al₂Cu) at the grain boundary are the strengthening phases of alloy, which provides the effect of dispersion strengthening and precipitation strengthening.