Abstract: The transformation behaviors of ironbearing minerals during O2/CO2 combustion of pulverized coal usere studied through combustion experiments of by burning wulanmulun coal and halagou coal in a drop tube furnace. 57Fe Mssbauer spectroscopy was employed to characterize and compare in detail the ironbearing components present in the ashes formed in O2/N2 and O2/CO2 combustion as well as those occurring in the parent coals. It was found that, in comparison with O2/N2 combustion, O2/CO2 combustion does not affect the ironbearing phases formed, however, it does affect their relative amounts in the ashes. O2/CO2 combustion favors the included pyrite and siderite to form ironcontaining glass silicates rather than oxidizing to form iron oxides. The changes of the relative amounts of the ironbearing phases in the ashes imply that O2/CO2 combustion may affect the potential of slagging. For the coals highly containing included ironbearing minerals, O2/CO2 combustion may enhance the slagging potential.