Aiming at the development of boron-containing ultra-thin fireproof coatings for steel structures, this paper mainly introduces that based on the basic formula of boron fireproof coatings, the general range of five kinds of fireproof additives such as zinc borate is determined by single factor choice test. A good formula for boron-containing ultra-thin steel structure fireproof coatings has been obtained through cross-testing. From the analysis of the test results, when the coating thickness is 1.1 mm, the fire resistance limit can reach 76 min 57 s, exceeding the requirement in GB 14097-2002 by about 17 min.