Combustion characteristics of Yi Min lignite and Zhun Dong lignite in o2lco2 atmosphere were inves- tigated by analysis. The effects of the coal type 2 concentration were studied. The results indicate that the increasing of o2 concentration can significantly improve the combustion performance especially when the O2 concentration is less than 60%. The activation energy corresponding to the YM lignite combustion in o2/N2 and O2/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 ju the degree of the reaction difficulty.