Abstract: Temperature-pressure-adsorption equation （TPAE） parameters were calculated based on a series of isothermal adsorption experimental data from medium rank normal coal and deformed coal in Pingdingshan No.5 mine. The results of TPAE show that the adsorption is a spontaneous exothermic reaction, and the desorption is not a spontaneous endothermic reaction. The thermodynamic calculation proves that when the adsorption amount increases, its unit isosteric enthalpy of desorption decreases according to the power function relationship. The unit isosteric enthalpy of desorption of normal coal is 2.2 times that of deformed coal. Coal absorbs environmental energy to desorb gas, reduce temperature, and increase pressure; rising pressure and lowing temperature are promoting the adsorption of coal, which results in a new gas liquid equilibrium. The direct consequence of the continuous increase of coal adsorption is the continuous decline of its unit isosteric enthalpy of desorption. The ambient energy input and the gas internal energy accumulation and transfer show mutual inducement and mutual reinforcement, until the new wave of environmental energy input, induce gas desorption to reach a high pressure gradient sufficiently to cause gas protrusion. The preparation, initiation, development, and termination of gas outburst are sequential processes. The segment node for separating outburst preparation and initiation is whether there is human engineering activity. The segment node for separating initiation and development is whether the wall of the system is broken. The segment node for separating development and termination is whether the adsorption amount of the deformed coal is close to zero.