For the global environmental preservation, the paper conducts an O2/CO2 combustion experiment on pulverized coal and studies an optimum O2/CO2 combustion technology system, for the purpose of developing a combustion system which minimizes pollutant emitted from coal-fired boilers. For basic research on CO2 recovery by oxygen combustion, carried out are dynamic simulation of the O2 generator, one-dimensional combustion simulation, O2/CO2 combustion tests and micro gravity combustion tests. When assuming amounts of raw material air and product oxygen to be disturbances, the O2 generator follows load fluctuations. In O2/CO2 combustion, less NOx is produced than in air combustion, that is, 60-70% NOx can be reduced as compared with air combustion because recycling NOx is reduced in the combustion field. SO2 also decreases, and most of the S content is found to be absorbed in the ash. In the micro gravity field, flames become dim and the flame propagation rate drops in the CO2 environment. The flame propagation rate becomes higher with increasing oxygen concentration. 4 refs., 185 figs., 25 tabs.