Abstract: In this paper, the microstructure evolution, mechanical properties and exfoliation corrosion behavior of Al-Zn-Mg-Cu alloys with different Cu contents ( 1.5 %, 2.1 %, 2.7 % ) at different quenching water temperatures ( 0 °C, 50 °C, 100 °C ) were systematically studied. The results show that the increase of Cu content significantly improves the quenching sensitivity of the alloy. With the decrease of quenching cooling rate, due to the higher thermodynamic driving force of phase transformation, the high Cu alloy undergoes severe non-uniform dissolution in the phase transformation sensitive temperature range, resulting in obvious Ostwald coarsening in the crystal and the precipitation of coarse and non-coherent equilibrium η phase. The large consumption of supersaturated vacancies and effective solute atoms leads to the transition of dislocation interaction to Orowan bypass mechanism, which weakens the precipitation strengthening effect in the artificial aging stage and leads to a significant decrease in yield strength. At the same time, the low cooling rate and high Cu characteristics accelerate the diffusion of Zn and Mg to the grain boundary, promote the continuous precipitation of Cu-containing high-activity anode phase at the grain boundary and broaden the non-precipitation zone, aggravate the expansion of intergranular corrosion, resulting in a significant deterioration of corrosion resistance. The performance test showed that when the quenching water temperature increased from 0 °C to 100 °C, the yield strength of 1.5Cu, 2.1Cu and 2.7Cu alloys decreased by 1.4 %, 2.2 % and 6.7 %, respectively, and the exfoliation corrosion grade decreased from EA⁺ to EB and EB⁻ to EC⁻ and EC⁻ to ED⁺.