Abstract: In an oxygen enriched pressure reactor, it was very important to present the molybdenite oxidation process using the curve about temperature and pressure. However, the measured temperature value could not reflect the gas temperature in reactor because of the influence of radiation and temperature rising. It was thus necessary to make a calibration to get the real gas temperature in reactor. An equation relating with environmental temperature, measured temperature and calibration temperature was set up based on the thermal equilibrium and general gas law. The parameters A and B were calculated through the empty reactor roasting experiment. As a result, the method of calibration temperature decided by the change of environmental temperature and the top measurement temperature of reactor was set up. The results showed that the equation fitted well with the real gas temperature. The relationship parameter R² was 0.915 in empty reactor roasting experiment. The molybdenite roasting process in an oxygen enriched pressure reactor was analyzed by this calibration method. The oxygen temperature was found to decrease during molybdenite oxidation in an oxygen enriched pressure environment. The reaction started obviously when the pressure was 0.262~0.276 MPa and temperature was 456~481 K.