The polyaddition of diglycidyl ether of bisphenol A (DGEBA) with phosphonic dichlrides was carried out using quaternary ammonium salt catalysts. Phenylphosphonic dichloride (PPDC) and phenylthiophosphonic dichloride (PTPDC) were used as dichlorides. Sulfone-containing PTPDC showed higher molecular weights than PPDC including oxygen. Thermo-oxidative stability of the sulfone-containing poly(phosphonate) showed lower wieght loss temperature than that of poly(phosphonate) without sulfone. But, sulfone-containing poly(phosphonate) had high char product of over 26 %, and UL-94V test confirmed its flame retanding capacity of V-0 rating by adding a little amount of anti-dripping material like teflon.