The invention relates to a Cu-Al2O3 nanometer dispersion strengthening alloy and preparation thereof. The preparation includes the steps of Cu-Al alloy vacuum smelting, pulverizing, screening, internal oxidizing, hydrogen reducing, vacuum hot pressing, canned hot extruding, etc. Comparing with oxygen-free copper, sigma of the alloy of the invention is 2 to 6 times higher that of the oxygen-free copper, the anti-annealing softening temperature is up to over 900 DEG C, the conductivity is up to 96% IACA and more. The process of the invention is simple, the prepared Cu-Al2O3 nanometer dispersion strengthening alloy has high strength, high conductivity, electrical conductivity higher than 96% IACA, and is anti-annealing and antimagnetic. The alloy can not only used for large-scale integrated circuit lead frame, manufacturing of controlled thermonuclear reaction heat sink components, and is expecially suitable for manufacturing of microwave tube grid mesh, inertial instrument sensor, particle accelerator and other high-precise parts.