The invention provides aluminum alloy for an automobile part. The aluminum alloy comprises the following components of Mg, Si, B, Ti, Cu, Cr, Zr, Fe, Sn, Co, Sc, Hf, and the balance Al and unavoidable impurities. Compared with the prior art, the Mg, Si, Cu, Cr and Zr elements are added into the aluminum alloy, so that the strength and toughness of the aluminum alloy are improved effectively; and through the Co, Sc, Hf, Ti and B elements added into the aluminum alloy, a die casting product can generate good grain refinement, the defect of casting cracks is overcome effectively, and the appearance of a casting and the surface quality of a cast ingot are improved. The invention further provides a die casting method for the automobile part, and the aluminum alloy for the automobile part is adopted. According to the aluminum alloy and the die casting method, the casting prepared through die casting, the defects such as pores or shrinkage cavities or misrun or unclear appearance outlines are overcome, and the product yield is high.