The invention discloses coating slurry for enhancing prestress of a building ceramic. The coating slurry consists of aggregate and an adhesive in a weight ratio of 1 to 4, wherein the aggregate is a combination of oxides, hydroxides and oxygen containing salts of Si, Al, Mg, Ca and Zn; the aggregate comprises the following chemical components: 50-75% of SiO2, 10-30% of Al2O3, 0-20% of MgO, 0-25% of CaO and 0-10% of ZnO; the adhesive is one or a combination of CMC (Carboxy Methyl Cellulose Sodium), PVA (Polyvinyl Acetate), PVB (Polyvinyl Butyral) and sodium silicate. In addition, the inventionfurther discloses a preparation method and a building ceramic product of the coating slurry. The coating slurry disclosed by the invention is adopted to completely coat the surface of a building ceramic blank, by exerting prestress, the strain that the ceramic blank is stressed and broken is increased, so that the strength and the performance of the building ceramic product can be greatly improved. The preparation and the application of the coating slurry are simple in production, easy to control, low in cost and beneficial to popularization and application, and have very high practical valuesand application prospects.