Novel phosphorus-containing binaphthyl epoxy DGEBN (diglycidyl ether of 2,2'-hydroxy-1,1'-binaphthalene) with high thermal performance was obtained from the addition reaction of DGEBN and diethyl phosphite. The modified binaphthyl epoxy was characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance spectroscopy. The dynamic mechanical property of the cured epoxy polymer was investigated by dynamic mechanical thermal analysis. The result revealed that the cured polymer with lower phosphorus content displayed higher value of the storage modulus when the networks reached rubbery state (above the glass transition temperature T-g). The T(g)s decreased slightly with increasing phosphorous content. The thermal degradation was studied with thermogravimetric analysis and the evolved gas was analyzed using thermogravimetric analysis/Fourier transform infrared technique. The influence of phosphorus content and the chemical structure on the degradation behavior was discussed. The P-modified binaphthyl epoxy polymers exhibited higher thermal stability than the P-modified diglycidyl ether of bisphenol A polymer. Flammability measurements were performed by the examination of limited oxygen index and UL-94 test. Compared with unmodified DGEBN, P-containing epoxy polymers displayed higher limited oxygen index values and exhibited better flame retardance. POLYM. ENG. SCI., 49:1879-1885, 2009. (C) 2009 Society of Plastics Engineers