Casting method of Al-Zn aluminium alloy

The invention belongs to the field of alloys and in particular relates to a casting method of an Al-Zn aluminium alloy. The casting method provided by the invention comprises the following steps: a) melt-blending an aluminium source, a copper source, a manganese source, a magnesium source, a chromium source and a zinc source to obtain an aluminium alloy melt, wherein the aluminium alloy melt comprises 1.4-2wt% of Cu, 0.2-0.6wt% of Mn, 1.8-2.8wt% of Mg, 0.1-0.25wt% of Cr, 5.0-6.5wt% of Zn and the balance of Al; b) preheating casting equipment; c) casting the aluminium alloy melt in the preheated casting equipment to obtain an Al-Zn aluminium alloy cast ingot. The flaw detection eligibility rate of the aluminium alloy cast ingot is increased by preheating the casting equipment before casting the aluminium alloy melt. Experimental results show that the flaw detection eligibility rate of the Al-Zn aluminium alloy cast ingot prepared by adopting the casting method provided by the invention is higher than 90%.