The relationship between the precipitation behavior and mechanical properties of Al-Zn-Mg-Cu-Zr aluminum alloys with low scandium (Sc) content (0.02%wt, 0.07%wt, 0.12%wt) was investigated by using optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), and universal material testing machine. With the increase of scandium content, the as-casting microstructure of the alloy is gradually refined, and the coarse secondary phase at the grain boundary increases, thus weakening the effect of fine grain strengthening. In the rolling +T6 state, the Al3(Sc, Zr) phase inhibit the precipitation of the main strengthening phase ηˋ, and the inhibition effect becomes more obvious with the increase of scandium content in the alloy, thus weakening the precipitation strengthening effect. The grain refinement in the alloy is conducive to the formation of more and fine dimples during the tensile deformation, improving the ductility of the alloy. The low Sc content alloy (0.02%wt) shows the excellent mechanical properties after rolling and T6 heat treatment, the tensile strength and elongation was measured as 683 MPa and 21%, respectively.