The invention discloses a preparation method of foamed aluminum. Aluminum chips are used as substrates, and are chips generated duringmachining of aluminum or aluminum alloys, so that the aluminum chips are easy to obtain and low in cost, and the production cost of the foamed aluminum is greatly reduced; and during preparing, the aluminum chips are put in treatment liquid and ethanol water solution in sequence for dipping to remove surface oil stains. Then, the aluminum chips are put in a heating furnace for heating to become molten aluminum; and a refining agent is added to remove remained impurities. An alterant, magnesium powder, chromium boride and molybdenum silicide are added; and then, hollow steel balls are preheated, and are put in the molten aluminum for dipping after preheating.The hollow steel balls attached with the molten aluminum are put in a mold, and are arranged in a face-centered cubic mode; the mold is preheated; the prepared molten aluminum is injected in the mold, and is put in an oven for insulation; and the mold is taken out to prepare the foamed aluminum. The foamed aluminum is higher in compressive strength and hardness, low in preparation cost and easy to popularize on the market.