The effect of quenching rate on the aging precipitation behavior and properties of Al-Zn-Mg-Cu-Zr-Er alloy was investigated. The scanning electron microscopy, transmission electron microscopy, and atom probe tomography were used to study the characteristics of clusters and precipitates in the alloy. The quench-induced η phase and a large number of clusters are formed in the air-cooled alloy with the slowest cooling rate, which contributes to an increment of hardness by 24% (HV 26) compared with that of the water-quenched one. However, the aging hardening response speed and peak-aged hardness of the alloy increase with the increase of quenching rate. Meanwhile, the water-quenched alloy after peak aging also has the highest strength, elongation, and corrosion resistance, which is due to the high driving force and increased number density of aging precipitates, and the narrowed precipitate free zones.