The invention belongs to the technical field of air purification, and relates to a building decoration material with the formaldehyde purification function and a preparation method of the building decoration material. The building decoration material is composed of the following components in parts by weight: 1-20 parts of a formaldehyde scavenger, 100 parts of a base material, 0.5-1 part of modified starch, 1-1.5 parts of a binder, 0.6-1 part of lignocellulose, 0.01-0.1 part of a foaming agent and 65-75 parts of water, wherein the formaldehyde scavenger is composed of the following componentsin parts by weight: 2-10 parts of polyvinylpyrrolidone, 1-6 parts of a water-soluble polymer compound, 4-42 parts of a chiral amino alcohol, 1-7 parts of titanium dioxide, 1-7 parts of tin dioxide, 1-7 parts of silicon dioxide, 2-6 parts of magnesium oxide, 1-13 parts of activated carbon, 1-9 parts of calcium chloride and 1-13 parts of a soluble weak acid salt. The building decoration material provided by the invention can quickly, stably, and highly efficiently purify formaldehyde, and is suitable for large-scale promotion and application.