The invention discloses a preparation method of an oil-proof aerated brick, and belongs to the technical field of building material. Cement, fly ash, ore powder, quartz sand, modified coarse aggregate, composite compacting agents, modified filler, water reducing agents and water are put into a material mixing machine; under the condition that the rotating speed is 100 to 200r/min, stirring and mixing are performed for 30 to 50min; mixed slurry is obtained; then, waste engine oil is sprayed into a mold; next, the mixed slurry is injected into the mold; after static mold stripping is performed for 5 to 10h, mold stripping is performed to obtain a brick blank; the brick blank is put into a steam curing kettle; under the conditions that the pressure is 2 to 3MPa and the temperature is 160 to 180 DEG C, heat preservation and pressure maintaining curing is performed for 10 to 18h; then, natural curing is performed for 5 to 10 days; the oil-proof aerated brick is obtained. The oil-proof aerated brick provided by the invention has excellent oil resistant performance and mechanical performance.