The water-based ultra-thin intumescent fire-retardant coating special emulsion was prepared by using thermosetting epoxy resin modified thermoplastic acrylic emulsion as film forming matter. By using FT-IR, DSC, TGA, SEM, the emulsion properties and the effect of emulsion on fireproof coatings were studied. The results show that:the decomposition temperature and glass transition temperature of emulsion membrane were enhanced by epoxy modified，so that it can be match with expansion system. Using epoxy resin modified acrylic ester emulsion as film forming material ,the coating can form a dense, uniform honeycomb bubble hole after thermal expansion, and it achieve good fireproof performance .