Abstract: In air or water ingress accident of the high temperature gas-cooled reactor (HTR), the corrosion of graphite components is inevitable result from oxygen and water steam ingression, that may affect the reactor safety. Oxidation progress and the gas products of IG-110 nuclear graphite were studied using gas chromatograph. The numerical simulations were carried out by THERMIX/REACT software. The results show that temperature has a marked impact on IG-110 graphite oxidation. As well as the content proportion of CO to CO₂, oxidation amount increases with temperature. The application of THERMIX/REACT for HTR safety analysis is validated by comparisons of the results of experimental and numerical simulation.