The invention discloses a low-temperature high-strength aluminum welding wire and a preparation method thereof. The aluminum welding wire comprises the following components by mass percent: 0.005% to 10% of Ag, 0.0005% to 1.0% of Be, 0.1% to 2.0% of Sc, 0.01% to 1.0% of Cd, 0.01% to 2.0% of Hf, 30% to 65% of Si, 0.01% to 3.0% of Ge, 5% to 15% of Nb, 0.01% to 0.5% of Ce and 0.01% to 0.5% of Cu, and the balance being Al. The preparation method comprises the steps of weighing the components according to mass percent; putting the components in a smelting furnace to be subjected to primary smelting for 3 h to 6 h at the temperature of 800 DEG C to 1200 DEG C; when the temperature drops to 650 DEG C to 750 DEG C, increasing the temperature to 1000 DEG C to 1200 DEG C, and carrying out secondary smelting for 1 h to 3 h; decreasing the temperature to 650 DEG C to 750 DEG C again, carrying out standing for 10 min to 20 min, and carrying out casting to obtain a casting; and removing impurities on the surface of the casting, and carrying out extrusion, wire drawing and scraping cleaning to obtain the aluminum welding wire. The aluminum welding wire obtained through the preparation method has good comprehensive performance, good welding performance and excellent room temperature cold forming performance.