The uniaxial tensile creep tests of Al–Cu–Mg alloy were carried out over a wide range of temperature and applied stress. The effects of applied stress and creep aging temperature on the precipitation in Al-Cu-Mg alloy were discussed. It is found that the precipitation process is very sensitive to the applied stress and creep aging temperature, and S phase (CuMgAl2) is the main precipitate under the tested creep conditions. With the increase of applied stress and creep aging temperature, S phase easily grows up and becomes sparse. Meanwhile, the creep aging leads to the discontinuous distribution of precipitation phase in grain boundary, which can improve the corrosion-resistance of Al-Cu-Mg alloy. Because the lattice misfit of acicular exudation phase is far less than that of disk-shaped phase, the applied stress/strain fields will alert the competitive precipitation equilibrium between different strengthening phases. So, the large applied stress and high aging temperature easily make the preferential precipitation process as SSS→GPB→S″→S′→S.