The catalytic activity of a salt mixture of potassium sulfate and nickel nitrate on the steam gasification of a bituminous char at 650-850 ℃ has been measured in an atmospheric thermobalance reactor. The mixture of K2SO4 and Ni(NO3)2 exhibits a synergic effect on the activity and the effect is more pronounced at low temperatures. Double the reaction rate could be obtained at 650 ℃ with the mixed catalyst. Although the activity of the mixture does not reach that of potassium carbonate which is known to be one of the best catalysts in coal gasification, the mixutre seems to be an economically favorable catalyst material in coal gasification. Of the three different gas-solid reaction models to evaluate the reaction kinetic parameters, the shrinking core model in chemical reaction controlled regime and the modified volumetric model well describe the gasification behavior. The apparent activation energy of non-catalytic gasification was found to be 99 kJ/mol and that of catalytic gasification 84 kJ/mol. The effect of heat treatment temperature for preparing coal char on the catalytic activity was also considered.