The invention discloses a cement concrete structure surface hidden paint. The cement concrete structure surface hidden paint is mainly prepared from, by weight, 39%-82% of a 30%+/-5% alkali metal silicate aqueous solution, 5%-10% of a 30%+/-5% methyl silicate aqueous solution, 1%-5% of nano-silica, 1%-10% of alkali metal hydroxide, 1%-5% of zinc oxide, 0.1%-1% of fluorinated surfactant, 0.02%-0.06% of fluorinated surfactant and 5%-30% of deionized water. The invention further provides a preparing method of the cement concrete structure surface hidden paint. In the cement concrete structure surface hidden paint and the preparing method thereof, raw materials and the resultant are all inorganic matter, the problem of organic ageing is avoided, and the hidden paint is environmentally friendly; the preparing method is simple, the cost is low, the paint is sprayed on the surface of a structural object without changing the original color, and the external appearance effect cannot be influenced.