Pressurized oxy-fuel combustion has been developed as a clean technology to realize higher efficiency and lower CO2 emissions. The combustion characteristics of a pulverized bituminous coal were investigated in a high-pressure optical accessible flat-flame reactor. The experiments were conducted in O-2/N-2 and O-2/CO2 environments. The tests were conducted at a gas temperature of 1400 K, under pressures ranging from 0.1 to 0.5 MPa, and at an oxygen concentration of 20%. An image processing technology was applied to investigate the processes of ignition, devolatilization, and burnout. The temperatures and diameters of individual burning particles were optically measured by a high-speed camera in conjunction with a long-distance microscope. A 532 nm continuous laser was used to trace the unburnt particles. The optical measurements were used to analyze the apparent kinetics of char oxidation using a commonly employed single-film char oxidation model. The results indicate that an increase in pressure causes a longer ignition delay time and a higher particle temperature. However, varying the pressure has no significant effect on char combustion kinetics. In the O-2/CO2 atmosphere, the reactivity of the entire combustion process is reduced and the apparent activation energy of char oxidation clearly increases compared to the O-2/N-2 atmosphere for the same pressure and oxygen concentration.