The invention discloses a light heat-preservation brick with leakage-proof and environment-friendly functions. In order to achieve the purposes, the light heat-preservation brick is provided with a heat-preservation layer and a waterproof layer. A cavity is formed in the middle of the heat-preservation layer and is filled with a foaming material. The heat-preservation layer is constituted by mixing magnesium oxide, magnesium chloride, sulfuric acid, perlite, limestone powder and water. The water leakage proofing layer is constituted by polyacrylate limestone powder and water. The thickness ofthe waterproof layer is 2-5 mm. The light heat-preservation brick has the advantages that the technical problems of water leakage proofing and heat preservation of a roof and reduction of the bearingpressure can be solved through one kind of the brick, construction is convenient, heat preservation and the small mass are achieved, and the water leakage proofing effect is good.