The effects of trace silver and magnesium additions on the microstructure and mechanical properties of the Al-Cu-Li alloys were investigated. The experimental results indicate that the effect of combined additions of Ag and Mg is the most obvious,the next is that of individual addition of Mg, and that of individual addition of Ag is the least. The addition of Ag and Mg in Al-Cu-Li alloy accelerates the precipitation of T1 and results in increasing the ageing hardness and strength. Prior cold work significantly improves the tensile strength by enhancing T1 precipitation in all the alloys investigated.