The combustion characteristics of sewage sludge have been investigated in a manufactured incinerate reactor. Two sludge samples that abolished by two difference site are applied to the experience. Heating value of sludges are 2600 ~ 3600 cal/g and there are about 80 wt% moisture contents. Moisture content of the sludge directly affects the heating value of the sludge and the flue gas composition. When reaction time goes to 10 minutes with 800 ℃, the combustion efficiencies were found to almost finished as few concentration of CO. Flue gas composition were CO, CO₂, NOx, SOx and HCl gas. It was found that the SOx and NOx concentrations in flue gas were increased as high temperture and long reaction time. Especially the SOx concentration was higher to relatively.