Abstract: The effects of single-stage solution and double-stage solution on microstructure and tensile properties of 7475 Al alloy have been investigated by transmission electron microscopy (TEM) and universal material testing machine. The results show that the optimal parameter of solution treatment for 7475 Al alloy is double-stage solution at 470 ℃/40 min + 500 ℃/25 min. After double-stage aging of 120 ℃/5 h+163 ℃/18 h, σ_b, σ_0.2 and δ are 499 MPa, 454 MPa and 12.9%, respectively. Compared with single-stage solution, the solid solubility of double-stage solution is significantly improved, the precipitation driving force increases, the critical nucleation size of the precipitated phase decreases, and the nucleation rate increases. After aging treatment, the number of matrix precipitates is more, and finer. Thus aging strengthening has been achieved.