The invention relates to the field of papermaking, and discloses a high-whiteness coated ivory board and a preparation method thereof. The high-whiteness coated ivory board comprises raw paper and a coating layer covering the surface of the raw paper, wherein the raw paper comprises a surface paper layer, a core paper layer and a bottom paper layer, the coating layer comprises a pre-coating layer, a surface coating layer and a back coating layer, the paper pulp of the raw paper comprises 80-90 parts of hardwood pulp and 10-20 parts of softwood pulp, the paper pulp is formed by bleaching treatment through a biological enzyme method, the coating materials of the pre-coating layer, each of the surface coating layer and the back coating layer comprises a pigment, a coating adhesive and a coating additive, the pigment comprises 85-95 parts of ground calcium carbonate and 5-15 parts of kaolin, and the coating additive comprises a fluorescent whitening agent accounting for 0.05-0.10% of the total weight of the coating materials. The preparation method comprises the steps of paper pulp preparation, net loading, squeezing and water removal, preliminary drying, on-line coating in a machine, drying and subsequent calendaring, reeling, cutting and packaging. The invention provides a method for preparing the high-whiteness coated ivory board by using a biological enzyme method for bleaching and using a small amount of a whitening agent, and the whiteness of the prepared coated ivory board is 94% or above.