Abstract: Thermal decomposition process and activation characteristics after different temperature thermal excitation of high calcium coal gangue, from Xinyang Coal Mine, are studied by the methods of thermal gravimetric analysis, conductivity and pH test, ICP-AES ion concentration detection experiment. The results indicate that the phase change of coal gangue shows four stages: volatilization of absorbed water, weightlessness stability, volatilization of structural water and organic carbon, mineral decomposition. And with the rise of activated temperature, conductivity, activated ion concentration will decrease in distilled water, and a high pH dissolution solution is formed; solution pH test shows that there will form a high pH, and strong polarity and alkali environment when high calcium coal gangue is dissolved in the distill water.