The co-combustion characteristics for Korean anthracites and bituminous coals were determined in a labscale CFB reactor and the commercial scale Tonghae CFB Power Plant. In the lab-scale CFB combustion tests, the effluent rate of the emission gases, which can indicate the reactivity of the combustion, did not change appreciably when each coal burned. As the bituminous coal was added, however, the effluent rate of the emissions increased. The amount of the unburned carbon in ash decreased with increasing the ratio of the bituminous coal during the co-combustion. When the co-combustion was tested in the Tonghae CFB power plant, the temperatures at the upper part of the combustor and the cyclones, which were somewhat higher than designed and expected, could be reduced as the bituminous coal ratio increased. Consequently, more stable operation of the CFB boiler was achieved. The efficiency of the CFB boiler also increased due to increasing the reactivity of the combustion.