The Al/Mg laminated composite was fabricated by an accumulative roll bonding (ARB) technique using Al-1100 and Mg-AZ31 at 573 K. Tensile properties along rolling direction under different ARB cycles were evaluated at the ambient temperature. The tensile strength of the Al/Mg composite increased gradually till three ARB cycle and then decreased after the fourth ARB cycles. Scanning electron microscopy (SEM) was used to investigate the microstructure evolution and the failure mechanism. The Al/Mg interface with interface angles between 30° and 35° has minimum tensile strength. A higher or lower interface angle improves the tensile strength, and the interface angle can be reduced by increasing the number of cycles in the ARB process. Thus, the crack at the coarse intermetallic compounds and rupture of the Al layer after fourth cycle caused the premature failure of the specimens during the tensile test.