The invention discloses high-temperature-resistant environment-friendly metal casting coating and a preparation method thereof. The coating comprises, by weight, 3-5 parts of attapulgite clay, 12-15 parts of quartz powder, 5-12 parts of talcum powder, 4-10 parts of superfine glass powder, 1.5-4 parts of sodium silicate, 3-5 parts of bauxite, 3-8 parts of diatomaceous earth, 2-4 parts of bentonite, 6-10 parts of polyethylene glycol, 3-9 parts of organic siloxane, 5-9 parts of silicon resin, 6-12 parts of linseed oil water-soluble alkyd resin, 4-6 parts of triphenyltin hydroxide, 2-6 parts of lignosulfonic acid, 1-3 parts of oxidizing agents, 1-2 parts of wetting agents, 2-5 parts of defoaming agents, 4-9 parts of preservatives, 2-6 parts of bonding agents, 5-8 parts of curing agents and 75-90 parts of deionized water. Compared with the prior art, the casting coating prepared through the method has excellent high temperature resistance, crack resistance and scouring resistance, and is good in adhesiveness and air permeability; meanwhile, the produced coating is uniform, environmentally friendly, free of pollution, good in stability and adsorbability, and capable of meeting the requirements for mass production of large castings, and improves the surface quality of the castings.