Abstract: Underground coal gasification（UCG） technology can achieve clean gas through controlling the combustion of coal seam underground.Based on the characteristics of coal seam gasification,char-steam reactions at elevated temperature are investigated kinetically using self-designed UCG-simulated gasifier.The effects of temperature,flow rate of steam and particle size of coal on gasification reaction are researched with relevant kinetic parameters.The results show that,in a certain range,with the increase of steam flow rate,the carbon conversion rate and gasification rate increase.The particle size of coal has a significant effect on gasification process,while no obvious change law is observed.The higher the gasification temperature,the shorter the time needed to reach the same carbon conversion rate.The constant of reaction rate k gradually increases with the rise of temperature,but reaction order shows the contrary trend.The results supply a theoretical reference to the optimization of process conditions in UCG.