The high temperature (HT) thermal stability and mechanical properties of Al-5%Cu (AC) and Al-5%Cu- 0.2%Mn-0.2Zr% (ACMZ) alloys from 573 to 673 K were systematically studied. The results displayed that micro-alloying additions of Zr and Mn elements have presented a significant role in stabilizing the main strengthening metastable θ′ precipitates at a temperature as high as 573 K. Simultaneously, the HT tensile test demonstrated that ACMZ alloy retained their strength of (88.6±8.8) MPa, which was much higher than that of AC alloy ((32.5±0.8) MPa) after the thermal exposure at 573 K for 200 h. Finally, the underlying mechanisms of strength and ductility enhancement mechanism of the ACMZ alloy at HT were discussed in detail.