Pyrophosphoric lactone-modified polyester containing two phosphorous functional groups in one structural unit of base resin was synthesized to prepare a nontoxic, reactive flame-retardant coatings. Then, the pyrophosphoric lactone-modified polyester was cured at room temperature with isocyanate and isophorone diisocyanate (IPDI)-isocyanurate to get a two-component polyurethane flame-retardant coatings (TAPPU). Comparing the physical properties of the films of TAPPU with the film of nonflame-retardant coatings, no deterioration of physical properties was observed with the incorporation of a flame-retarding component into the resin. Three kinds of flame retarding tests were conducted, including the 45 degrees Meckel burner method, limiting oxygen index method (LOI method), and oxygen combustion method with Cone calorimeter. It was observed that the char lengths were 3.1 similar to4.5 cm and LOI values were 27 similar to 30%. These results indicate that the prepared coatings are good flame-retardant ones. It was also found that the flame retardancy of those coatings was increased with the contents of phosphorous.