The invention provides an exothermic catalytic combustion method for a pyrolysis gasification submelting furnace under pure oxygen conditions, which is characterized in that pure oxygen is directly introduced into the pyrolysis gasification submelting furnace for pyrolysis after the ignition. During the pyrolysis, catalysts, namely magnesium powder, aluminum powder or a mixture of the magnesium powder and the aluminum powder is added from the furnace bottom, and the adding amount of the catalysts is between 0.1 and 1.0 kg for each ton of treated substance. During the pyrolysis gasification, the pressure in the furnace is adjusted by adjusting the opening degree of a rectification mechanism to ensure that the pressure inside the pyrolysis furnace is stable. The method has the advantages of low cost, energy conservation, and environmental protection.