The invention discloses a formula of anti-mildew paint, which is composed of cement, quartz sand, heavy calcium powder, light calcium carbonate, lime calcium powder, talcum powder, anti-cracking fiber and additives, and the weight ratio of each component is cement 19 %, quartz sand 28%, heavy calcium powder 29%, light calcium carbonate 6%, ash calcium powder 12%, talcum powder 4%, anti-crack fiber 1.5%, additive 0.5%; the additive is hydroxypropyl methylcellulose , preservatives, fungicides and light stabilizers. The anti-mildew paint of the present invention is stirred with a mixer to form a dry mixture, which can be used after adding a certain proportion of water and stirred at the construction site, and can be constructed by spraying or scraping. The coating of the present invention has strong adaptability to mildew-prone environments, has the advantages of antibacterial and anti-mildew effects, moisture resistance, water resistance, strong adhesion, etc., and generally can reach a service life of more than 10 years. The invention also provides a preparation method of the paint.