To study the compatibility of polymers and liquid oxygen, four types of epoxy resins with different chemical structures were selected, and then were copolymerized with cyanate ester. Thermal analysis was conducted on the cured compounds for oxidation weight gains analysis, oxidation decomposition weight losses analysis, flash points, etc. Then the compatibility of the cured compounds with liquid oxygen was contrasted with liquid oxygen impact sensitivity. The oxidation and combustion properties of the cured compounds are consistent with their compatibility with liquid oxygen. Polymers with better anti-oxidation show better compatibility with liquid oxygen. This conclusion helps us see deeper into polymers' compatibility with liquid oxygen, instructs us to select or design polymers compatible with liquid oxygen. Furthermore, besides the liquid oxygen impact test, thermal analysis can play an important role in charactering polymers' compatibility with liquid oxygen.