Abstract: The temperature will induce thermal stresses in the coal body and lead to fractures and even an abruption, which might improve the gas extraction. Based on the finite element software RFPA, the process of fracturing during heating is simulated, and the evolution of coal fracturing at different temperatures is revealed. Using the acoustic emission technique, the internal fissures of the coal are identified under different temperatures and confining pressures. The results are compared and it is shown that the thermal stress generated by the temperature can raise the coal temperature, destroy the original cleat system, and produce new cracks. When the temperature reaches to a certain value, the porosity fracture of the internal coal expands, the main cracks are formed, the effective penetration channel is enlarged, the adsorption capacity of the coal is reduced, the content of the free gas is increased, and the penetration is significantly increased. The work might provide some insight in preventing the mine disaster due to the gas, and also for the gas extraction.