A novel epoxy system was developed through the in situ curing of bisphenol A type epoxy and 4,4-diaminodiphenylmethane with the sol-gel reaction of a phosphorus-containing trimethoxysilane (DOPO-GPTMS), which was prepared from the reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) with 3-glycidoxypropyltrimethoxysilane (GPTMS). The preparation of DOPO-GPTMS was confirmed with Fourier transform infrared, 1H and 31P NMR, and elemental analysis. The resulting organic-inorganic hybrid epoxy resins exhibited a high glass-transition temperature (167 °C), good thermal stability over 320 °C, and a high limited oxygen index of 28.5. The synergism of phosphorus and silicon on flame retardance was observed. Moreover, the kinetics of the thermal oxidative degradation of the hybrid epoxy resins were studied. ; JNL0002919