The invention relates to a method for manufacturing aluminum alloy die forgings, in particular to a method for manufacturing AL-Cu-Mg alloy die forgings. The method for manufacturing the aluminum alloy die forgings of over-length and ultra-large dimension aluminum alloy propeller blades is provided, so that the strength, abrasion resistance, corrosion resistance and fracture toughness of the propeller blades are improved, and the service life of the blades is prolonged. The method includes the following steps that first, an aluminum alloy ingot casting is heated; second, a wedge-type workblank is machined; third, a forging piece is obtained; and fourth, the forging piece is subjected to corrosive washing degrease, neutralizing and white washing in an acid tank, quenching and heat preservation and single-stage aging, and accordingly the aluminum alloy die forgings can be obtained. The die forgings of the over-length and ultra-large dimension aluminum alloy propeller blades manufactured by the method not only can meet the standard requirement but also can improve the usability of the propeller blades, the characteristics of strength, abrasion resistance, corrosion resistance, fracture toughness and the like of military propeller blades are improved, and the service life of the propeller blades is prolonged.