The invention belongs to the technical field of aluminum alloy casting and particularly discloses high-strength cast aluminum alloy. By means of the high-strength cast aluminum alloy, the problems that in the prior art, an aluminum alloy casting is low in structural compactness and prone to segregation, and comprehensive performance including strength, toughness and plasticity is poor are solved.A preparation method comprises the following steps of adding Si, Mg, Zn, Cu, Mn, Ti, RE and Sn into a metal smelting furnace, conducting high-temperature melting, so that alloy melt A is obtained, andconducting heat preservation for use; after high-temperature melting of the Al is completed, adding a refining agent for refining, so that pure molten aluminum B is obtained; adding the alloy melt Ato the pure molten aluminum B, adding SiC and alterant, and mixing the materials to be uniform, so that molten alloy C is obtained; and completing casting of the molten alloy C at the high temperature, so that a casting is obtained. By means of the high-strength cast aluminum alloy, structural compactness of the casting is effectively improved, and the casting segregation problem is avoided; and the obtained aluminum alloy is high in strength and hardness, good in wear resistance and corrosion resistance, good in machining and casting performance and wide in application prospect.