The invention mainly relates to the field of coatings, in particular to an automotive OEM (original equipment manufacturer) intermediate coat with high solid content and low viscosity and a preparation method of the intermediate coat. The intermediate coat comprises raw materials in percentage by mass as follows: 25%-35% of polyester resin, 5%-12% of anti-sagging resin, 15%-25% of rutile titanium dioxide, 0-2% of hollow glass microspheres, 12%-18% of superfine precipitated barium sulfate, 1%-3% of a dispersing agent, 0.1%-0.3% of white carbon black, 0.1%-0.3% of an organosilicon leveling agent, 0.3%-0.6% of an acrylate leveling agent, 0.2%-0.5% of a surfactant, 0-2% of an anti-settling agent, 0-4% of cyclohexanone, 3%-5% of ethylene glycol monoethyl ether acetate, 0.05%-0.2% of carbon black, 20%-28% of butylated amino resin and 2%-4% of partial methylated amino resin. The intermediate coat is low in applicable viscosity, good in appearance, economical and environment-friendly and has high content of applicable solids.