The invention relates to a high silicon aluminum alloy and a preparation method thereof. The technical proposal adopted is as follows: the high silicon aluminum alloy comprises the following components by weight percentages: 69.5-73.5% of aluminum, 19.0-21.0% of silicon, 4.5-5.5% of copper, 0.5-0.7% of magnesium, 0.8-1.0% of iron, 0.8-1.2% of zinc, 0.2-0.4% of manganese, 0.03-0.08% of nickel, 0.1-0.2% of titanium, 0.2-0.4% of bismuth and 0.1-0.15% of impurities. The preparation method comprises the following steps: the reclaimed aluminum scrap is used for batching after being detected, the batched materials are put into a smelting furnace for melting at the temperature of 900-950 DEG C for 4-6 hours; and the product high silicon-aluminum alloy is obtained after adjusting the furnace charge, modification, refining, slag removal and casting. The high silicon-aluminum alloy can lower electric energy consumption and cost, can reduce the environment pollution and has a simple preparation process.