The invention relates to aluminum alloy used for preparing an engine cylinder cover and a preparation method for the aluminum alloy and belongs to the field of aluminum alloy. Raw materials are prepared according to percentages of 6.5%-8.5% of silicon, 2%-3% of copper, 0.4%-0.6% of iron, 0.2%-0.3% of magnesium, 0.15%-0.45% of manganese, 0.1%-0.15% of titanium, 0.1%-0.25% of zirconium, 0.01%-0.015% of europium, 0.002%-0.004% of gadolinium, 0.01%-0.015% of neodymium, and the balance aluminum. The raw materials are heated to 820-845 DEG C to be molten, helium preheated for 2-3 min is led into the raw materials in the molten state from the bottom of a container, slag and dross are removed, standing is conducted for 20-30 min, then the raw materials are poured into a mold, a primary-prepared cylinder cover is obtained, quenching treatment is conducted at 490-510 DEG C, and aging treatment is conducted at 160-220 DEG C. The aluminum alloy is good in heat dispersion and corrosion resistance, thus the cylinder cover is not liable to various damage, the gas tightness is good, and the service life of an engine is prolonged.