The invention relates to a building sealant. The building sealant is prepared from the following components in parts by mass: 100 parts of hybrid resin, 0 to 20 parts of plasticizer, 100 to 400 parts of calcium carbonate, 0 to 3 parts of ultraviolet absorbent, 2 to 12 parts of silane coupling agent, 3 to 10 parts of silane crosslinking agent and 0 to 3 parts of catalyst. The building sealant has the beneficial effects that 1, the environment-friendly and non-toxic effects are realized, the emission of VOC (volatile organic compound) is zero, the harm to environments and human bodies is avoided, and the building sealant is a green product; 2, the construction technology is simple, the extrusion property is good, and the sagging and collapsing are avoided; 3, after curing, the adhering property on tiles, marbles and the like is good, the pollution to the tiles is avoided, the flatness is high, the color and luster is bright, the certain toughness is realized, the flushness of the tile joint and the tile surface is ensured, and the hollow and loosening are prevented; 4, after curing, the color is fresh, fine, smooth and uniform, and multiple colors can be matched according to requirements; 5, the waterproof and moistureproof effects are realized, the blackening and mildewing are avoided, the dirt is avoided, the cleaning is easy, and the building sealant is very suitable for high-grade workplaces of hotels, discos hall, luxury real estates, conference rooms and the like.