The information on the processes of volatile combustion and devolatilization is important in designing and operating the combustor of solid waste fuels of which volatile proportion in the combustible is very high. The aims were to compare the reactions of the waste fuels having different origin and to sort out their own distinguishable characteristics that are important in designing the FBC(fluidized bed combustor). Waste fuels were selected to examine their characteristics of pyrolysis and combustion in a laboratory scale combustor in which a nearly single particle combustion condition was reproduced. Wood, paper sludge, sewage sludge and RDF were selected and the fuel particles whose characteristic lengths were a few centimeters were injected into a fluidizing environment of 700 ℃ sand in the thermally maintained reactor. By introducing some experimental parameters such as the rate and the fraction of carbon conversion, the combustion characteristics of the fuels were checked for the two separated processes of devolatilization and char combustion. Additional experimental work was carried out to determine the influence of the high water content of sludge fuels on its combustion process. The comminution effects on the combustion process of the large fuel particle were rechecked by performing the experiments for the wood particles of various size. The meanings of the fuel combustion characteristics in designing of FBC were checked and some design strategies were suggested.