The invention discloses a variable oxygen partial pressure environment high temperature heat radiation performance test device, and a test method. According to the test method, a high temperature aerobic test environment with controllable temperature and oxygen partial pressure is established on the surface of a sample, so that accurate test on material high temperature heat radiation performanceat variable oxygen partial pressure environment is realized; a variable oxygen partial pressure high temperature gas purging system is used for forming oxygen/nitrogen mixed gas purging gas flow on the surface of the sample, realizing real-time controlling of the oxygen partial pressure and gas absolute pressure of the heating environment of the sample, avoiding influences of heat radiation signals emitted by polar molecules such as water and carbon dioxide in atmosphere at high temperature on test results, and ensuring heat radiation test accuracy; synchronous heating and constant temperaturecontrol of purging gas and the sample are adopted, so that heat convection effect between the sample surface and the purging gas is inhibited effectively, and accurate temperature control of the sample surface temperature is ensured.