In order to more accurately analyze the coal rock degradation arising from gas adsorption, a new method was proposed based on particle discrete element theory. The degradation test and numerical simulation were used to verify the applicability of this method. The particle discrete element analysis for the degradation effect on coal rock showed that: The gas adsorption on the surface of coal rock particles favored to reduce the surface free energy of coal rock particles, but would decrease the contact bond tensile strength and effective modulus of coal rock partides; meanwhile, the expansion stress generated by gas adsorption would cause weakening of the coal rock particle contact bond cohesive force. The micro key parameters of bonding and internal friction angle in numerical simulation were corresponded with that in the macro degradation test one by one. These findings provide a new approach for studying the gas adsorption-induced degradation of coal rock. (C) 2019 Elsevier B.V. All rights reserved.