Pyrophosphoric modified polyesters (TATBs) were synthesized by polycondensation of adipic acid, trimethylolpropane, 1,4-butanediol, and tetramethylene bis(orthophosphate). Two-component PU flame-retardant coatings (TATBCs) were prepared by blending TATBs with HDI-Biuret. Most of the physical properties of the flame-retardant coatings were comparable to those of non-flame-retardant coatings. Coatings containing 10 and 15wt% 1,4-butanediol, TATBC-10C and TATBC-15C were not flammable in the vertical flame-retardancy test.