Abstract: Using a reasonable analysis model, the oxidation of graphite IG-11 used in 10MW High Gas Temperature Cooled Reactor （HTR-10） was investigated. In this paper, the oxidation quantity of reflector graphite by oxygen at maximum temperature in HTR-10 was calculated. The calculation results showed that the oxidation amount increased with the CO quanta in reaction product. When the reaction product was only CO, the maximum theoretical corrosion thickness of graphite was 35.8mm.When the reaction product was only CO₂, the minimum theoretical corrosion thickness of graphite was 23.7mm. During the service life of graphite, the oxidation of reflector graphite at maximum temperature was serious.