The carbonization of magnesium oxide particles by CO2 was investigated using a stirring mill reactor. The effects of the system temperature, stirring rotation speed, influx rate Of CO2 and initial diameter of the magnesium oxide particles on the carbonization process were determined. The results show that the system temperature and the stirring rotation speed are the most significant influencing factors on the carbonization rate. The determination of critical decomposition temperature (CDT) gives the maximum carbonization rate with other conditions fixed. A theoretical model involving mass transfer and reaction kinetics was presented for the carbonization process. The apparent activation energy was calculated to be 32.80-mol(.-1). The carbonization process is co-controlled by diffusive mass transfer and chemical reaction. The model fits well with the experimental results.