This paper studies for the effect of solution-aging (SA), homogenization + solution aging (H+SA), Hot isostatic pressing + solution-aging (HIP + SA) three different heat treatments on the microstructure and mechanical properties of selective laser melting (SLM) formed Inconel 718 alloy. The as-built Inconel 718 has a large number of dendritic structures, and there are many brittle Laves phase precipitating among the interdendritic region. The δ phase was prone to precipitate when treated by proper homogenization, but the material can not be strengthened without γ"and γ " phases. Hot isostatic pressing(1080 ℃×1480 bar/2 h) can considerably removed Laves phase and micro pores of the as-fabricated samples, and combine with the solution aging treatment subsequently, it’s conductive to refine the grain size of the as-built samples, flat the grain boundaries, and promote the precipitation of γ "、γ " phase, so HIP+SA treatment significantly increases the strength of Inconel 718 alloy, the mechanical properties of Inconel 718 alloy reached their optimum combination at UTS=1361 MPa, 0.2% YS=1191 Mpa, and HV0.2 =490, and the elongation after breaking is 13.30%.