The invention relates to a preparation method for Fe-Mn-Al alloy, and belongs to the technical field of lightweight and high strength alloy preparation. The preparation method comprises the steps that by weight, 12.0-14.0% of Al, 18.0-30.0% of Mn and the balance Fe are mixed evenly and proportionally; mixed powder is subjected to tabletting and then is smelted under the protection of inert gas, melts are continuously stirred in the smelting process, and when the temperature of alloy melts reaches 1520-1550 DEG C, a water-cooling copper mold is adopted to cast a sample; the obtained sample is subjected to heat preservation at the 1000 DEG C for 2-3 hours under the protection of inert gas and then subjected to oil quenching, alloy after oil quenching continues to be heated to 550-650 DEG C at the atmosphere of inert gas and subjected to tempering treatment, after heat preservation is conducted for 2-4 hours, the alloy is cooled to the indoor temperature along with a furnace, and the Fe-Mn-Al lightweight and high strength alloy is obtained. The method is relatively simple and reliable, and the prepared Fe-Mn-Al alloy is high in strength, light, good in oxidation resistance and good in corrosion resistance.