The invention discloses a high-Zn, high-Mg and low-Cu ultrahigh-strength corrosion-resisting aluminum alloy and a heat treatment method. The alloy comprises the following components by mass percentage: 6.5-8.3% of Zn, 2.3-3.0% of Mg, 0.8-1.2% of Cu, 0.1-0.2% of Zr, less than 0.15% of Fe, less than 0.1% of Si, and the balance of Al. A preparation method of the alloy comprises the steps of blending, smelting, semi-continuous casting, homogenizing, thermoplastic deformation, short time solid solution, and ageing heat treatment. For the high-Zn, high-Mg and low-Cu ultrahigh-strength corrosion-resisting aluminum alloy prepared with the method, the hardness (HV) is 185-209, the tensile strength sigma b is greater than or equal to 650Mpa, the percentage elongation delta is greater than or equal to 7%, the pitting resistance is high, the cast ingot yield is high, and the stress corrosion resistance is further improved while the mechanical property is kept after multiple regression reageing treatment. The alloy and the heat treatment method solve the problems that the cast ingot yield in the existing high-copper Al-Zn-Mg-Cu ultrahigh-strength aluminium alloy is low, and the strength, toughness and corrosion resistance cannot be compromised. The heat treatment method is simple to operate, and the industrial production is facilitated.