In this paper, Al-5.6Zn-2.8Mg-1.6Cu-0.24Cr-1.1Li, Al-8.0Zn-2.4Mg-2.4Cu-1.1Li-0.18Zr and Al-11.8Zn-2.9Mg-2.8Cu-1.1Li-0.24Zr (in wt%) alloys were artificially aged at 80,100,120,140 and 160°C for different time, respectively. The ageing process, microstructure and hardness of different alloys are investigated by Vickers hardness and transmission electron microscopy (TEM). With the increment of zinc content, addition of Li to Al-Zn-Mg-Cu alloy containing high alloying elements has little effect on the nucleation of precipitates, but the growth of precipitates has been inhibited. Very fine precipitates with high density are formed during ageing due to the existence of high alloying elements, which result in highly strengthening alloy. As the alloying content is too high to exceed the solution saturation of matrix, coarse second phases are formed in grain boundary.