The invention discloses a preparation method of a water-based high flash aluminum pigment for automobiles. The method comprises the steps of putting spherical aluminum powder, steel balls as grinding mediums, environmentally friendly solvent oil, oleic acid or erucic acid, and a surfactant into a ball mill, sealing the ball mill, performing ball milling, discharging with the environmentally friendly solvent oil, conveying the materials into a vibrating sieve through a pipeline to sieve, removing screen tailings, performing filter pressing to obtain filter cakes with the solid content being of 80 percent, putting the filter cakes and alcohol or ether solvents with good water compatibility into a reactor for mixing and dispersing, sealing the reactor, increasing the temperature under the protection of inert gases, then dropping water-soluble high polymer monomers and azo-initiators, increasing the temperature after the dropping is finished, holding the temperature, discharging, and performing filter pressing to obtain finished products. The method has the advantages that the environmental protection effect is good; the coating is tight, and a coating layer is difficult to be damaged; the water solubility is good, and the pigment can be directly diluted with water; and the pigment is easy to dissolve in water-based automobile paint systems, and is beneficial to the dispersion of the aluminum pigment.