The invention discloses a Al/Cu/Mg composite sheet rolling preparation method. The method comprises the following steps (1) homogenization treatment is carried out on aluminum alloy or pure aluminum billets, and magnesium alloy billets; (2) slotting is conducted on the corresponding position of the aluminum alloy or the pure aluminum billets, the magnesium alloy billets and a horizontal copper net; (3) oxide layers on the surfaces of the aluminum alloy or the pure aluminum billets, and the magnesium alloy billets are removed, surface coarsen treatment is carried out, then absolute ethyl alcohol is added to an ultrasonic cleaner to clean and dry, and impurities at the composite material interface joints are removed; (4) the billets are stacked in the order of the aluminum alloy or the purealuminum billets, the horizontal copper net, the magnesium alloy billets, the horizontal copper net, the aluminum alloy or the pure aluminum billets, and a vertical copper net is inserted into a stacked billet groove to form composite billets; (5), cold rolling is carried out; (6) hot rolling is carried out; and (7) ply rolling is carried out. The Al/Cu/Mg composite sheet material rolling preparation method can improve the interface bonding strength of a magnesium and aluminum composite plate, and enhance the impact toughness of materials, so that the integrated mechanical performance of composite materials is improved.