Combustion characteristics of Yi Min lignite and Zhun Dong lignite in O-2/CO2 atmosphere were investigated by thermo-gravimetric analysis. The effects of the coal type and O-2 concentration were studied. The results indicate that the increasing of O-2 concentration can significantly improve the combustion performance especially when the O-2 concentration is less than 60%. The activation energy corresponding to the YM lignite combustion in O-2/N-2 and O-2/CO2 atmospheres was evaluated by two isoconversional methods. The calculation results showed that further research is required whether the activation energy calculation with isoconversional methods for complex reaction process can be used as a basis for judging the degree of the reaction difficulty. (c) 2012 Elsevier B.V. All rights reserved.