A phosphorus-containing epoxy resin was synthesized successfully by 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) and bisphenol F epoxy resin (DGEBF) and its molecular structure was confirmed by FTIR spectra. The results of the liquid oxygen mechanical impact test indicated that the cured phosphorus-containing epoxy resin did not show any reactions during the 20 times of mechanical impact, which revealed that it was compatible with liquid oxygen. Thermal properties of the cured epoxy resins were evaluated by differential scanning calorimetry and thermal gravimetric analysis. It was found that the cured phosphorus-containing epoxy resin had a better thermal stability than DGEBF. The enhancement of thermal stability for the epoxy resin was favorable to improve liquid oxygen compatibility. The X-ray photoelectron spectroscopy analysis confirmed that the mechanical impact resulted in phosphorus-containing groups on the surface of the cured phosphorus-containing epoxy resin thermally decomposed to form phosphoric oxyacid which was in accordance with the mechanism that organo-phosphorus compounds could work in the condensed phase to inhibit the combustion. These results suggest that the phosphorus-containing epoxy resin has the potential as the matrix of the liquid oxygen composite tank. POLYM. ENG. SCI., 55:651-656, 2015. (c) 2014 Society of Plastics Engineers