Combustion characteristics both of paper and sewage sludges have been studied in a 0.5 mI.D×3.35 mH fluidized bed. The maximum temperature along the height was found and maintained near the surface of fluidized bed during the combustion. The paper sludge containing water about 59.8% of water could be burned without auxiliary fuel, while the auxiliary fuel was required to incinerate the sewage sludge, which containing about 79.3% of water. The stable operation status could be monitored by the mean pressure and the standard deviation of pressure fluctuation signal. The mean pressure near the surface of fluidized bed decreased with the increase of sludge feed rate. On the other hand, the standard deviation of pressure fluctuation increased with the increase of sludge feed rate. The emission of CO decreased with oxygen content in the flue gas, while that of NOx increased with the oxygen content.