Abstract: The characteristics of sulfur release during HT-coal combustion in the mixed-CO2 gas with different concentrations of oxygen were studied. The results show that during combustion in low oxygen concentration flow the rate curves of H2S and SO2 present two clear peaks, the quantity of released H2S increases and the whole time of sulfur release is prolonged. On the contrary, during combustion in high oxygen concentration flow the rate curves of H2S and SO2 show single peak, the time of sulfur release shortens. Because of improvement of self-capturing sulfur ability of the ash, the quantity of sulfur release is reduced during combustion in the mixed-CO2 gas with low oxygen concentration. The quantity of sulfur release from coal burned in high oxygen concentration flow is close to that burned in the air flow.