The invention discloses fire-retardant paint and a preparation method thereof, and belongs to the technical field of chemical engineering paint processing. The fire-retardant paint is prepared by dissolving the following ingredients in parts by weight into a solvent: 100 to 120 parts of epoxy resin, 20 to 30 parts of modified polyamide acid solution, 15 to 20 parts of filling materials, 10 to 15 parts of fire-retardant filling materials, 5 to 15 parts of pigments, a coupling agent solution, 0.5 to 1 part of dibenzoyl peroxide, 0.5 to 1 part of N,N-dimethylaniline, 0.05 to 0.1 part of imidazole promoters and amine curing agents, wherein the equivalent ratio of active hydrogen in the amine curing agents to epoxy groups in the epoxy resin in the paint is 0.45 to 0.55. The modified polyamide acid solution prepared from castor oil, isocyanate, tripolycyanamide and anhydride is used for modifying the epoxy resin; the prepared paint has good coating performance and can be fast cured at low temperature; after the curing, the bonding performance of the coating is good; the toughness is good; the fire-retardant effect is good.