Abstract: In order to further study the pyrolysis kinetics characteristics of low metamorphic coal in situ fluid mining process, differential scanning calorimetry and flash method was used to investigate the characteristics of specific heat capacity and thermal diffusion coefficient of lignite evolving with temperature. The results show that both the specific heat capacity and thermal diffusion coefficient of lignite increase first and then decrease with the temperature rising, and the obvious threshold temperature is obtained. Based on the analysis of lignite thermal weight loss characteristics, it can be seen that the relationship between the change of lignite weight loss and the specific heat capacity evolution is obvious. The thermal diffusion coefficient of lignite is affected by the constituent phase in the coal and is proved to be anisotropic characteristics. It is concluded that the variation of lignite composition and content is the internal cause of the complex variation of thermodynamic parameters under the temperature effect. And the mechanism of water phase transition and thermal decomposition determines the evolution of thermodynamic parameters with temperature rising.