Abstract: The effect of annealing treatment on the interfacial structure of Cu-Ce/Al-Mg alloy composite strips was investigated in this paper. No interfacial phase was formed after annealing at 200 ℃ and 250 ℃. When the annealing temperature was 350 ℃, intermetallic compounds CuAl₂ and Cu₉Al₄ were observed at the interface. Increasing the annealing temperature to 450 ℃ resulted in the formation of a new intermetallic compound, CuAl. The results indicate that a critical temperature exists for the intermetallic compound phases at the Cu-Al interface, and the types of interfacial phases increase with the increase of annealing temperature. At a constant annealing time, the thickness of the interfacial layer increases with the increase of annealing temperature. At a constant annealing temperature, extending the annealing time does not increase the types of intermetallic compounds in the interfacial layer, but the interfacial layer thickens. Compared with pure Cu/Al composite plates, the Mg element in the Al-Mg alloy improves the thermodynamic stability of CuAl₂ during the annealing process, restricts the transformation of CuAl₂ into CuAl, and leads to a decrease in the growth rate of the CuAl layer.