The effect of precipitation microstructure change on the stress corrosion behavior of AA2024 aluminum alloy was investigated by constant load stress corrosion tests, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the T3 alloy is much more sensitive to stress corrosion than the T8 alloy. The corrosion process and precipitation microstructure change of T3 and T8 alloys were investigated by in-situ corrosion observations operated by high-angle annular dark-field scanning TEM (HAADF-STEM), which intuitively demonstrate the different corrosion morphologies: the corrosion morphology of T3 alloy is intergranular corrosion and that of T8 alloy is a combination of intergranular corrosion and grain attack. Because of the change in precipitation microstructure and corrosion mechanism, the alloys with different ageing conditions possess different stress corrosion susceptibility.