The invention discloses high-strength anti-corrosion aluminum alloy and a preparation method thereof. The high-strength anti-corrosion aluminum alloy comprises, by weight, 4.5-5.5% of Mg, 0.9-1.8% of Zn, 0.4-1.0% of Mn, 0.01-0.05% of rare earth Ce, 0.15-0.35% of Er, 0.10-0.25% of Zr, 0.01-0.06% of B, 0-0.1% of impurity Si, 0-0.15% of Fe, 0-0.15% of other impurity elements, and the balanced element Al. the preparation process of the aluminum alloy comprises the steps of raw material proportioning, raw material smelting, refining, pouring, three-stage homogenizing treatment, compressional deformation treatment, tensile deformation treatment and aging treatment. The preparation process is simple and easy to implement and low in production cost. The aluminum alloy has high corrosion resistance and good mechanical properties.