Abstract: Phosphorous-containing flame-retardant ploy(ethylene terephthalate) was prepared by incorporation CEPPA-EG which had been pre-synthesized from 2-carboxyl ethyl(phenyl) phosphinic acid(CEPPA) and ethylene glycol(EG) into the precondensate of bis-2-hydroxyethyl terephthalate (BHET).With the help of IR,SEM,DSC,TGA and LOI,the structure,thermal,flammable and char forming properties of the product were investigated.The results indicated that the flame retardants were copolymerized into the PET chain.With the content of flame retardants increasing,the T_c of flame-retardant polyesters increased,while T_g and T_m showed a decreasing tendency.The flame-retardant property of polyesters also enhanced,as demonstrated by higher LOI and more uniform char granule.