The invention belongs to the technical field of a decorative material and discloses formaldehyde-removing antibacterial seaweed mud paint. The formaldehyde-removing antibacterial seaweed mud paint comprises 18 to 32 parts of water, 0.5 to 0.8 part of dispersing agent, 0.8 to 1.2 parts of antifreezing agent, 0.8 to 1.5 parts of film forming assistant, 10 to 25 parts of titanium dioxide, 15 to 20 parts of calcium carbonate, 5 to 8 parts of kaolin, 2 to 6 parts of mica powder, 0.15 to 0.3 part of nanometer Ag antimicrobial, 3 to 8 parts of seaweed mud, 0.3 to 0.5 part of thickener, 0.3 to 0.8 part of negative ion additive, 15 to 30 parts of odor-purifying emulsion, 0.15 to 0.3 part of mould inhibitor, 0.2 to 0.3 part of preservative and 0.1 to 0.2 part of water repellent agent. The invention also discloses a preparation method of the formaldehyde-removing antibacterial seaweed mud paint. The formaldehyde-removing antibacterial seaweed mud paint disclosed by the invention is fine and smooth in hand feeling and has strong water repellency and good durability; the surface of a paint film is smooth and fine; the formaldehyde-removing antibacterial seaweed mud paint has efficient antimicrobial and mould-proof functions; formaldehyde is efficiently adsorbed and decomposed and odor is removed; indoor humidity is automatically regulated; the formaldehyde-removing antibacterial seaweed mud paint not only overcomes the defects of a common internal wall latex paint on the aspects of adsorbing and decomposing formaldehyde, removing odor and the like, but also solves the problems that a seaweed mud coating can only adsorb formaldehyde, but cannot decompose formaldehyde, is rough in hand feeling and the like.