The invention discloses a heat-insulating coating for a building, belonging to the technical field of heat-insulating coatings. The heat-insulating coating comprises the following raw materials: 320-380kg of common silicon white cement, 420-480kg of quartz sand, 180-220kg of ground limestone, 2-4kg of cellosilk, 28-32kg of vitrified micro bubbles, and 18-22kg of colloidal crystal, and all the rawmaterials are uniformly mixed when the coating is manufactured. The heat-insulating coating has the beneficial effects that: 1, the sunscreen effect and the heat-insulating effect are good, the solarradiation energy can be reflected by more than 85%; 2, the integrated functions of waterproofing, heat insulation and heat preservation are achieved; 3, the cost performance is high, and the manufacturing cost per square meter can be reduced by 10-15RMB; 4, the construction is simple, the coating is suitable for waterproofing, seepage proofing and heat insulation of various housetop roofs, and the coating can be applied to construction simply after being added with water and uniformly mixed; and 5, the coating has the advantages of favorable weather resistance, corrosion resistance, ageing resistance, favorable caking property, difficulty in shedding, environment friendliness and use safety, and can be used for greatly prolonging the service life of the roofs and wall surfaces.