Abstract: The influence of reaction pressure on the sintering temperature of potassium carbonate loaded coal ash was investigated in H₂O-H₂-CO-CO₂ atmosphere. An empirical equation for sintering temperature calculation was derived based on the content of ash, the ash composition, the catalyst loading and the reaction pressure. The deviation between the calculated value and the experimental value was within ±15 ℃ (2%). The transformation of two coal ashes was investigated by X-ray diffractometer and thermodynamic calculation. It was found that potassium carbonate could react with anhydrite and calcite in coal to produce potassium sulfate and butschliite. The potassium sulfate and hematite could be reduced in the H₂O-H₂-CO-CO₂ atmosphere, and the decomposition temperature of butschliite increased with the increase of pressure. Moreover, the content of potassium hydroxide in the potassium loaded coal ash increased with the increase of temperature and pressure. The minimum sintering temperatures of coal ash under different pressures were related to the content of potassium hydroxide; when the contents of potassium hydroxide in ashes reached to a certain value, the calculated minimum sintering temperature was very close to the experimental one under different pressures.