The characteristics of Huadian oil shale combustion in O-2/CO2 atmospheres were compared to those in O-2/N-2 atmospheres by using non-isothermal methods. The combustion kinetics parameters were calculated using the Kissinger-Akahira-Sunose (KAS) and Friedman methods. Specifically, the effect of oxygen concentration (10, 20, 30, 50, 65 and 80% O-2) and heating rate (2, 5, 10 and 20 degrees C min(-1)) on the combustion reactivity and kinetics of Huadian oil shale in CO2-based and N-2-based atmospheres were investigated to identify the optimal gases mixture and oxygen concentration. Comparison of the combustion performances of oil shale in CO2/O-2 and N-2/O-2 environments indicated that the organic matter combusted earlier in CO2-based atmospheres than in N-2-based atmospheres when the oxygen concentration was 10% and 20%. Meanwhile, the average activation energies of organic matter combustion in CO2-based atmospheres was higher than those in N-2 -based atmospheres at an oxygen concentration of 10% and 20%. With an appropriate amount of O-2 and CO2, the combustion performance of oil shale in 30% O-2 /70% CO2 was superior to that in 30% O-2 /70% N-2, and the combustion activation energy in the 30% O-2 /70% CO2 atmosphere was also lower. The similar combustion processes and activation energies of oxy-fuel and conventional combustion with oxygen concentrations above 50% indicate that oxygen plays a leading role in organic matter combustion under high oxic conditions. The results reveal that the 30% O-2/70% CO2 atmosphere is optimal for oil shale combustion.