The invention discloses corrosion-resistant nylon fiber autoclaved aerated concrete and a preparation method thereof. The method comprises the steps that 1, oleic acid, triethanolamine and water are subjected to first mixing, and soluble oil is obtained; 2, an aluminum source, a foaming agent and water are subjected to second mixing, and an aluminum powder suspension is obtained; 3, polyvinyl chloride, polystyrene, Chinese herbal medicines, cyclohexanone, zinc acetylacetonate, aluminum nitride, 3-aminopropyltriethoxysilane and dioctyl adipate are subjected to heating melting to be prepared into a plastic wood melt; 4, cement, lime, pulverized fuel ash, gypsum, nylon fibers, phenolic resin, red brick particles, ferroferric oxide and water are subjected to third mixing in the presence of a magnetic field with the magnetic field intensity ranging from 0.002 T to 0.003 T, the soluble oil and the aluminum powder suspension are added for fourth mixing, pouring is conducted, and the corrosion-resistant nylon fiber autoclaved aerated concrete is obtained through aerating. Building materials prepared from the corrosion-resistant nylon fiber autoclaved aerated concrete have excellent mechanical strength and freezing resistance.