The effects of content of Mn, Si, Zn, Cu and Ce-rich mixed rare earth on the room-temperature mechanical properties and high temperature sagging resistance of the aluminum alloy on the basis of chemical composition of 3003M aluminum alloy were studied by orthogonal test. The chemical composition of aluminum alloy core material for composite aluminum foil was optimized and the sagging resistance mechanism of the aluminum alloy during brazing was analyzed. The results show that Cu element had the greatest effect on the tensile strength of the tested aluminum alloy, while Si, Mn and Cu elements had significant effects on the sagging resistance. The mass fractions of Mn, Si, Zn, Cu and Ce-rich mixed rare earth of the aluminum alloy with the best properties were 0.5%, 2.5%, 0.8%, 1.2%, 0, respectively. The tensile strength of the optimal aluminum alloy was about 40 MPa higher than that of 3003M aluminum alloy, the elongation increased by about 2 percentage points, and sagging distance was shortened by half. During brazing at 610℃, the secondary recrystallization occurred in the optimal aluminum alloy, and the microstructure was composed of dispersed precipitated phase, primary recrystallization grains and coarse long grains with size of about 1 mm.