The invention relates to a method for preparing a water-based mono-component transparent thermal insulating glass coating. The method comprises the following steps of: (1) preparing a polyurethane substrate; and (2) placing, mixing and stirring 50 to 90 weight parts of polyurethane substrate, 10 to 20 weight parts of nano metal oxide, 3 to 5 weight parts of aid and 5 to 25 weight parts of water in a container to prepare the transparent thermal insulating glass coating. The method has the advantages that: the method has the advantages of simplicity, easily obtainable materials, low cost, simple and convenient operation and easy popularization; and the coating has the advantages of high visible light transmission rate, ultraviolet rejection rate, near infrared rejection rate and surface hardness, long service life, strong adhesive force, high hydrolytic resistance and ideal thermal insulation effect.