A UV-curable polyurethane (PU)-coating system containing phosphorus is formulated by the combination of photoinitiator, PU acrylate oligomer, and UV-reactive phosphazene monomer. PU acrylate oligomer is prepared by the addition of 2-hydroxy-ethylmethacrylate (HEMA) to NCO-terminated PU prepolymer. UV-reactive phosphazene monomer is derived from the HEMA substitution reaction to hexachlorocyclotriphosphazene (NPCl2)(3). The curing reaction of this PU-coating system is carried out by UV irradiation. The resultant UV-cured PU-coated films demonstrated better performance properties than those of original UV-cured PU acrylate (UV-PU) without UV-reactive phosphazene monomer. Furthermore, their thermal properties are investigated by a thermogravimetric analyzer and a dynamic mechanical thermal analyzer, respectively. The combustion behaviors of these UV-cured PU-coated films are evaluated by the measurements of a limiting oxygen index and a cone calorimeter.