The invention discloses an anti-pollution flashover coating and a preparation method thereof. The anti-pollution flashover coating consists of the following compositions in part by weight: 20 to 40 parts of hydroxyl-terminated polyorganosiloxane, 4 to 8 parts of modified silicon fluorine resin, 1 to 3 parts of small molecular siloxane, 3 to 6 parts of nanometre silicon dioxide, 1 to 3 parts of decabromdiphenylethane (DBDPE), 1 to 3 parts of wollastonite, 4 to 8 parts of aluminium hydroxide, 1 to 2 parts of pigment, 1 to 6 parts of crosslinker, 0.02 to 1 part of catalyst and 30 to 60 parts of solvent, wherein the small molecular siloxane is trimethyl end-capped polydimethylsiloxane; the catalyst is dibutyltin dilaurate or stannous octoate; and the solvent is a mixed solvent of dimethylbenzene and butyl acetate in a weight ratio of 3:1-5:1. The prepared coating has the advantages of high flame retardant grade and good anti-pollution effect.