In the previous study it was found that the nickel catalyst impregnated on brown coals shows excellent activity in the gasification reaction. In this study more cheap catalyst, Ca (OH) 2, was used as starting material. The chemical state during the steam gasification was determined and the reactivity was determined in the temperature range from 600 to 800°C. Ion-exchanged Ca was transformed to finely dispersed CaCO3 upon pyrolysis and the extensive crystal growth of CaCO3 was observed during the course of steam gasification. Near the end of gasification CaCO3 was converted to CaO owing to the decrease of CO2 content in the atmosphere. About 2 wt% of Ca content was enough to enhance the reactivity of coal by a factor of 10 at 650°C. In order to obtain the same reaction rate, 750°C is necessary without catalyst. This catalytic effect was more significant when compared with the data for the Ca-catalyzed gasification of American low-rank coals.