Hydroxyethyl acrylate-phenyl-diethyl phosphoramide (APEEA) was prepared using phenyl phosphonic dichloride, hydroxyethyl acrylate and diethylamine as the raw materials. A series of core-shell particles with the average diameter about 0.08～0.1μm were prepared via seeded emulsion polymerization. The core-shell structure with APEEA and butyl acrylate as core, methyl methacrylate as shell was measured by transmission electron microscopy (TEM) analysis. The thermogravimetric analysis (TG) results indicated that the thermal stability and charring residue of the core-shell particles was increased by adding APEEA. The microscale combustion calorimeter results showed that APEEA can significantly improve the fire performance of the core-shell particle. Comparing with core materials for the particles of pure acrylic ester, the peak heat release rate was decreased by 55% with 15wt.% APEEA. The char-forming reaction of APEEA is the major factor of improving the particle combustion properties.