A method for making a metal-based nano-composite material is disclosed. In the method, a semi-solid state metal-based material is provided. The semi-solid state metal-based material is stirred and nano-sized reinforcements are added into the semi-solid state metal-based material to obtain a semi-solid state mixture. The semi-solid state mixture is heated to a temperature above a liquidus temperature of the metal-based material, to achieve a liquid-metal-nano-sized reinforcement mixture. The liquid-metal-nano-sized reinforcement mixture is ultrasonically processed at a temperature above the liquidus temperature by conducting ultrasonic vibrations to the liquid-metal-nano-sized reinforcement mixture along different directions at the same time.