The invention belongs to the field of materials and particularly relates to a plastic alloy. The plastic alloy is prepared from the following substances in parts by weight: 35-45 parts of 6-tert-butyl-3-methylphenol, 5-15 parts of acrylonitrile, 8-25 parts of styrene, 25-35 parts of butyl acrylate, 55-65 parts of polymethyl methacrylate, 3-5 parts of molybdenum, 15-25 parts of magnesium, 2-5 parts of chromium, 5-12 parts of lithium, 1-5 parts of cobalt, 1.5-2.5 parts of nickel, 1-3 parts of vanadium, 5-10 parts of compatibilizer and 5-10 parts of carbon. The plastic alloy provided by the invention has the advantages of high impact strength, good heat resistance, low hygroscopicity, small coefficient of linear expansion, excellent dimensional stability, good toughness, high strength and high corrosion resistance.