The invention discloses an anti-bacterial inner wall coating and a preparation method thereof, and relates to the field of building materials, wherein the anti-bacterial inner wall coating includes the following raw materials in parts by weight: 8-15 parts of acrylic ester, 5-10 parts of modified coral powder, 4-9 parts of titanium dioxide, 6-12 parts of diatomite, 3-7 parts of bamboo charcoal powder, 2-5 parts of anti-bacterial powder, 0.8-1.8 parts of redispersible latex powder, 3-7 parts of polyvinyl alcohol, 1-3 parts of cetyl sulfopropyl betaine, 0.2-0.6 part of an antifreezing agent, 0.4-0.8 part of a film-forming auxiliary agent and 15-20 parts of water. Through synergistic effect of the raw materials, the inner wall coating has the advantages of good corrosion resistance, temperature resistance and weather resistance, good anti-bacterial performance, purification of indoor air, high processing performance and easy coating construction.