The invention discloses a green, environmentally-friendly, waterproof, antibacterial and mildew-resistant decoration coating and a preparation method thereof. The decoration coating comprises, by weight, 30-40 parts of polyamine resin, 15-25 parts of butyl acrylate, 10-16 parts of polyvinyl alcohol, 4-8 parts of a modified nano-additive, 8-10 parts of ore powder, 2-4 parts of a mildew inhibitor, 1-3 parts of a botanical bactericide, 4-6 parts of hollow ceramic microbeads, 2-4 parts of reinforced fibers, 1-3 parts of titanium dioxide, 5-7 parts of a flame retardant additive, 6-9 parts of a processing enhancing additive and 18-24 parts of deionized water. The coating has the advantages of excellent hydrophobic and impermeable performances, good film forming performance, smooth and fine surface, certain sterilizing, bacterium-killing and mildew-resisting effects, realization of greenness and environmental protection due to the use of the botanical antibacterial and mildew-resistant additives, safe and reliable raw material components, no toxic or harmful volatile substances, low cost, simple process, high practical values and good application prospect.