The invention provides a high-stability antifouling automobile coating and a preparation method thereof, and belongs to the field of coatings. The high-stability antifouling automobile coating provided by the invention is prepared from modified organosiloxane, bismuth metallate salt and an amine curing agent, wherein the organosiloxane is prepared from a modifier and polymethylhydrogensiloxane; the modifier is selected from diallyl phthalate, diallyl-o-phthalate and diallyl terephthalate; the amine curing agent is selected from N, N-diethylcyclopentane-1, 2-diamine, 1-N-morpholino-2-amino-cyclopentane and 2-(4-methyl-1-piperazine) cyclopentylamine. The automobile coating provided by the invention has good corrosion resistance, aging resistance and antibacterial property.