The invention discloses a concrete brick with a good heat-preservation effect. The concrete brick comprises the following raw materials in parts by weight: 80-120 parts of calcined kaolin, 25-35 partsof building wastes, 8-16 parts of coal cinder, 20-30 parts of a silicon nitride compound, 20-30 parts of a polyurethane resin, 130-150 parts of cement, 8-16 parts of a gypsum powder, 10-20 parts of coal gangue, 8-16 parts of a glass fiber, 10-20 parts of a sepiolite powder, 10-20 parts of gravel, 2-4 parts of a polyacrylonitrile-based carbon fiber, 2-4 parts of precipitated barium sulphate, 2-4 parts of calcium chloride and 80-140 parts of water. The silicon nitride compound is prepared by using the following processes: uniformly mixing urea, formaldehyde and water, adjusting the pH value ofthe system to 8-8.4, adding nano silicon nitride and tetrabutyl titanate, heating and stirring, uniformly mixing with lecithin and N,N-dimethyl formamide, adding polyethylene, carrying out ultrasonicdispersion, filtering, washing, and drying filter residues, so as to obtain the silicon nitride compound.