Provided are an epoxy-resin intumescent fire-resistant coating for steel structure use, and a method for fabrication thereof, belonging to the field of functional coatings. The present intumescent fire-resistant coating consists of two components: A and B; component A mainly comprises a film-forming substance, dehydration and carbon-forming catalyst, a blowing agent, a carbon-forming agent, a promoter, a solvent, and a pigment and filler; component B mainly comprises a curing agent, modified polyethylenimine, a solvent, and a promoter. The fire-resistant coating uses diethyl-phosphite modified polyethylenimine as a fire-resistant additive (PEI-DEPP) and compound technology, effectively increasing the expansion ratio of the carbon layer and the quality of the carbon layer after the fire-resistant coating is burned. The coating has excellent fire resistance, adhesive force, water resistance, heat resistance, corrosion resistance, and acid resistance, and not only may be used for a high-rise steel structure building, but is also suitable for use in fire protection of steel structures in harsh environments, such as the marine equipment and petrochemical industries.