Abstract: The precipitation features of different phase fields in Al-Cu-Mg alloys were introduced.The effect of trace Ag on microstructure and mechanical properties of Al-Cu-Mg alloys were summarized.Addition of trace Ag is known to modify precipitation processes in Al-Cu-Mg alloys with different Cu/Mg ratios,to promote the formation of new phase that has better thermal stability,so that their response to strength and heat-resistant properties is enhanced.