The one-step ageing behavior of a novel Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr alloy was studied by measuring the mechanical properties and electrical conductivity, and the evolution of microstructure during the aging was investigated by using TEM. The results show that the aging response rate was greatly accelerated with elevating the aging temperature from 100 ℃ to 160 ℃, and the time achieved to over-aged stage was remarkably decreased, while the electrical conductivity of the alloy became higher. After aging for 14 h at 140 °C, the UTS, TYS, Elongation and Electrical conductivity values were achieved to 585 MPa, 560 MPa, 16.1% and 22.6 MS/m, respectively; Comparing with the T6 temper condition performed at 120 ℃ for 24 h, the UTS decreased only by 1%, whereas the TYS and the electrical conductivity obviously increased by 4% and 11%, respectively. The major strengthening precipitates of the peak-aged alloy were the η’ phase and GP zones. The precipitates in both the matrix and the grain boundary became coarser with rising aging temperature. There were obvious PFZs along the grain boundary when the aging treatment was performed at 140 ℃