Combustion characteristics of coal gangue under O-2/N-2 mixtures with different O-2 concentrations and coal mine methane (CMM) conditions were investigated by using thermogravimetric analysis (TGA) and tube reactor tests. Calculation results for the combustion characteristic parameters show that ignition temperature, burnout temperature, and peak temperature increase, while the maximum and average combustion rates decrease with decreasing O-2 concentrations. The mass loss decreases and comprehensive combustion characteristic index increases slightly when CH4 is present in the combustion atmosphere with equivalent O-2 concentration. TGA and tube reactor tests indicate that the mass loss of coal gangue is mainly attributed to the combustion of volatile matter and of fixed carbon. A temperature rise to similar to 650 degrees C markedly inhibits carbon combustion because of O-2 consumption caused by combustion of CH4 and H-2 produced from CH4 cracking. Kinetic parameters (apparent activation energy (E), reaction order, and frequency factor) were calculated for various atmospheres by direct linear regression of the kinetic equation from a single TGA curve. The E value of coal gangue combustion varies from 117.6 to 137.4 kJ/mol under different atmospheres, and is slightly higher in CMM than in the O-2/N-2 mixture with equivalent O-2 concentration.