The invention relates to an ultraviolet-resistant radiation-protection aqueous ultra-thin fire resistive coating for a steel structure and a preparation method thereof. On the basis of adopting an ethylene-vinyl acetate emulsion and a polyvinyl acetate emulsion as matrix emulsions, through also adding an ammonium polyphosphate, melamine, dicyandiamide, pentaerythritol, zinc borate, expandable graphite, a light stabilizer and water as raw-material components for the fire resistive coating, the prepared and obtained fire resistive coating is enabled to be not only good in flame resistance, high in heat insulation and excellent in fire resistive performance and but also have advantages of good ultraviolet resistance and anti-radiation performance, good weather resistance and the like; the fire resistive coating provided by the invention is used in the steel structure; the adhesiveness with a matrix is high; the coating has weather-resistant, ultraviolet-resistant, anti-radiation and waterproof functions, and is good in comprehensive performance. The fire resistive coating provided by the invention can be used for an indoor steel structure, and accords with to a GB14907-2002 Fire Resistive Coating for Steel Structure; the fire resistance rating reaches 2h.