The invention discloses nano modified water-borne coating and a preparation method thereof and relates to the technical field of coating production. The nano modified water-borne coating is prepared by, by weight, 27-40 parts of water-borne fluorocarbon emulsion, 1-5 parts of silane coupling agent, 1-5 parts of talcum powder, 1-5 parts of mica powder, 1-5 parts of nano titanium dioxide, 1-5 parts of propylene glycol monomethyl ether, 1-5 parts of adherence promotor, 1-5 parts of wetting agent, 1-5 parts of defoaming agent, 1-5 parts of filler, 1-5 parts of surfactant, 1-5 parts of fire retardant, 1-5 parts of antibacterial agent, 1-5 parts of water-borne wax, 1-5 parts of coalescing agent, 1-5 parts of thickening agent, 1-5 parts of polypropylene oxide glycol, 1-5 parts of potassium silicate, 1-5 parts of lauryl dimethyl amine oxide, 1-5 parts of buckwheat extract and 10-15 parts of deionized water. The nano modified water-borne coating has the advantages that by the reasonable components and proportion, the coating is good in coating film levelling property, high in weather resistance and high in artificial aging resistance, and the performance of the coating is increased by about 70% as compared with that of traditional coating.