Abstract: Wood-based structure has low fire resistance levels and large fire loads. Once a fire occurs, it will cause serious fire accidents. Transparent fire-retardant coatings are widely used to enhance the fire safety of ancient buildings due to their excellent decorative properties and fire resistance properties. Phosphorus-based flame retardants are widely applied as the main component of transparent fire- retardant coatings due to the advantages of environmental friendliness, high efficiency, low toxicity, etc.. This paper summarizes the research progress of phosphorus-based flame retardants in transparent fire-retardant coatings from the aspects of phosphate ester flame retardants, phosphorus-nitrogen flame retardants and composite phosphorus flame retardant. Research pointed out that the development of multifunctional modified phosphorus flame retardants, the realization of three sources in one, organic and inorganic phosphorus flame retardants, and the synergistic flame retardancy of multiple elements are the development trend of transparent fireretardant coatings in the future.

Key words: transparent fire- retardant coating, phosphate ester flame retardants, phosphorus-nitrogen flame retardant, composite phosphorus flame retardant