Understanding the reaction mechanism of oxy-coal combustion is fundamentally important to the CO2 capture and storage in coal-fired industrial processes. In this paper, the microscopic reactive behaviors of brown coal combustion in O-2/CO2 atmosphere were simulated by combining the molecular dynamics (MD) simulations and the reactive force field (ReaxFF). With thoroughly tracing the motion trajectories of atoms, as well as the formation, transition and breaking of bonds between atoms, the generation pathways of CO2 and the effects of temperature (1600-2000 K) and oxygen concentration (21%similar to 30%) on the coal oxy-fuel combustion process were studied. Results showed that the main process of CO2 generation consists of the decomposition, oxygenation, and dehydrogenation. The atmosphere with a high concentration of CO2 can accelerate the reaction rate of coal combustion and reduce the consumption of O-2. The higher temperature will promote the production of major intermediates with more fragments being released earlier, and finally increase the generation of CO2. The increase of O-2 concentration obviously hastens the decomposition of coal molecule and the generation of H2O, but shows very weak influence on the distributions of other major products and intermediates. (C) 2019 Elsevier B.V. All rights reserved.