According to retrogression and re-ageing treatment (RRA), a novel retrogression and stress-ageing treatment (RSA) is put forward for Al-Zn-Mg-Cu alloys. The effect of stress-ageing time and external stress on precipitates of pre-retrogressed Al-Zn-Mg-Cu alloy is investigated by transmission electron microscope (TEM). It is found that there is a large number of matrix precipitates (MPts) and slightly discontinuous grain boundary precipitates (GBPs) in the pre-retrogressed alloy. The effects of stress-ageing time and external stress on precipitates of the retrogressed alloy are significant. With the increase of stress-ageing time and external stress, the size of MPts increase and the density of MPts decreases. Meanwhile, the size of GBPs, the distance between GBPs and the width of precipitate free zone (PFZ) increase. Compared with the traditional retrogression and re-aging treatment, the retrogression and stress-ageing treatments increase the size of MPts, narrows the width of PFZ and discontinuous the GBPs of the studied Al-Zn-Mg-Cu alloy.