The automotive waterborne metallic flash basecoat was prepared by aqueous saturated polyester resin as matrix resin, methylated amino resin as a crosslinking agent, water-based flash aluminum powder as effect pigment, modified ethylene-vinyl acetate copolymer wax emulsion as directional alignment agent, and it is refined by substrate wetting agent, defoamer, leveling agent, neutralizer, thickener, cosolvent and deionized water. The film is cured at 160 ℃ for 20 minutes, it has some advantages such as low VOC content, high hardness, impact resistant, strong adhesion, good flash, excellent corrosion resistance, environmental protection, construction safety and convenience, etc.