The microstructures and mechanical properties of retrogression and re-aging (RRA) treated ultrahigh strength Al-Zn-Mg-Cu-Zr alloy containing Sc were investigated using transmission electron microscopy and tests for tensile properties and electric conductivity. The results show that the alloy maintains similar strength of T6 state and presents high conductivity after RRA treatment of (120 oC, 24 h pre-ageing) +( 180 oC, 30 min retrogression) + (120 oC, 24 h re-ageing); the intercrystalline microstructures are similar to those of the T6 state alloy and the grain boundary precipitates are aggregated and coarsened, similar to those of duplex over-aged microstructure.