Large amounts of massive cracked intermetallic compounds were observed at the interface of the laminated Mg/Al composite fabricated by accumulative roll bonding. Scanning electron microscopy revealed that the effect of these cracked intermetallic compounds dominated the fracture behavior of the accumulative roll bonded Mg/Al composite during uniaxial tensile testing. The results indicated that (i) obvious Mg/Al interface delamination was promoted by the cracked the intermetallic compounds, and (ii) the crack propagated into the softer Mg layer and leading to the rupture of Mg layer. These two factors led to premature failure of the laminated Mg/Al composite.