The invention discloses a frost-crack-resistant, waterproof and weather-proof building coating and a preparation method thereof. The building coating comprises the following components in parts by mass: 15-25 parts of polyvinyl alcohol, 15-25 parts of polyacrylate emulsion, 10-20 parts of silica sol, 10-20 parts of polyamide, 10-20 parts of quick lime, 10-20 parts of castor oil, 10-20 parts of potassium oxide, 10-20 parts of zinc oxide, 5-15 parts of aluminum oxide, 5-15 parts of polyvinyl acetate, 5-15 parts of methyl methacrylate, 10-20 parts of phenolic resin, 5-15 parts of ground limestone, 5-15 parts of bentonite, 15-25 parts of nano-silica, 15-25 parts of poly(vinylidene fluoride) resin, 15-25 parts of acrylic resin, 10-20 parts of diethylene glycol monobutyl ether, 10-20 parts of xylene, 5-15 parts of saturated hydroxyl terminated polyester resin, 3-5 parts of an antifoaming agent, 3-5 parts of a plasticizer, 3-5 parts of a dispersing agent, 3-5 parts of a fast dry agent, 3-5 parts of a coalescing agent, 3-5 parts of additives and 25-45 parts of deionized water. The building coating disclosed by the invention has the advantage that the waterproof effect and the like are improved, and can be constructed on base planes of multiple humid or dry materials; the building coating is excellent in waterproof performance, non-toxic and harmless, and meets the actual application requirement.