Effect of Ag content on the evaluated-temperature mechanical properties of a series of Al-Cu-Mg-Ag alloys was studied by means of tensile tests, endurance tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that tensile strength and ultimate endurance strength increased dramatically with Ag content increasing. SEM observations suggest a plastic transgranular manner of tensile fractures. TEM results reveal that increasing Ag content promoted the nucleation of the Ω phase, which was the dominant strengthening phase in matrix. Furthermore, Ω precipitates were not coarsened on a large scale after long time endurance at evaluated temperature.