An Al/Mg/Al composite with a trilaminate structure was fabricated by hot rolling and its mechanical properties at quasi-static rates of strain were investigated. The bonding strength of the trilaminated composite is about 40 MPa, mainly attributing to the mechanical bond at the interfaces. The first layer failure strength of the laminated composite increases from 305 to 372 MPa when the relative thickness of aluminium alloy layer increases from 0.235 to 0.265. The tensile and bending properties of the laminates were calculated based on the Classical Laminate Theory (CLT). The calculations of first layer failure strength based on CLT agree with the experimental data in the error of 2.9-18%. Thus, the first layer failure strength of the Al/Mg/Al trilaminated composite fabricated by hot rolling can be calculated by CLT with the maximum stress criteria. The calculations also show that the tensile modulus, the tensile rigidity, the specific tensile rigidity and the first layer failure strength of the laminated composite increase almost linearly with the relative thickness of the aluminium alloy component. The bending rigidity of the laminated composite increases with the relative thickness of aluminium alloy, and approximates to a fixed value after the relative thickness over 0.3. The specific bending rigidity increases with the relative thickness of aluminium alloy and reaches a maximum value when the relative thickness is 0.25.