The invention discloses a preparation method of an automobile engine crankshaft through powder metallurgy. The preparation method comprises the following process step of preparation of the following raw materials in parts by weight: 70-72 parts of iron powder, 1.3-1.8 parts of molybdenum powder, 1.3-1.8 parts of zinc oxide, 4.5-5.5 parts of stearic acid, 1.4-1.8 parts of tantalum carbide, 1.4-1.6 parts of silicon nitride, 1.2-1.5 parts of nickel powder, 2.2-3.4 parts of tungsten powder, 1.5-1.9 parts of cerium fluoride, 0.3-0.5 part of graphite powder, 1.3-1.6 parts of an inhibition phase and 1.5-1.8 parts of a lubricant, wherein the inhibition phase is prepared from the following raw materials in percentage by mass: 4-7% of NbC, 20-22% of VC, 13-15% of TaC, 8-10% of graphene and the balance being carbon powder. The preparation method disclosed by the invention has the advantages that a special proportioning of the raw materials is adopted, so that the performance index of produced products is high, the lustrousness is good, the stability is high, the phenomena of cracks and the like are not liable to occur, and the service life is long.