Reduction kinetics of magnesia with carbon powder was studied using the thermal gravimetric technic in the temperature range of 1743-1883 K. The reduction ratio was determined as a function of time. The effects of compact-forming pressure, composition, partial pressure of CO2 sample height, and temperature on reduction ratio were investigated, Experimental results revealed that the gas diffusion including Mg vapor, CO and CO2 through the porous medium was the rate- determining step of the overall reduction process. Activation energy of the gas diffusion was estimated to be about 30.59 kJ mol(-1).