The characteristics of mixed-firing of an anthracite and a bituminous coal were studied in a fluidized bed combustor(0.155m-I.D., 2.2 m-height). The used domestic anthracite coal has heating value of 2,010 kcal/kg and the imported high-calorific bituminous coal has heating value of 6,520 kcal/kg. The physicochemical analysis and the pressure fluctuation properties were measured to interpret the combustion characteristics in a fluidized bed combustor of uniform particles of mixed anthracite and bituminous coal is a function of the particle size ratio and the anthracite mixing fraction. The combustion characteristics of mixed fuels in a fluidized bed combustor could be interpreted by using standard deviation of pressure fluctuations, mean pressure and power spectrum density function. The different burning region of fluidized bed combustor was measured by the pressure fluctuation properties.