Power generation from Refuse Derived Fuel (RDF) is a promising utilization technology for municipal solid waste. To explain the combustion behaviors of RDF burnt in a fluidized bed incinerator, the commercial sized RDF was fed continuously in to a 0.3x0.3 mx2.73 m in height bubbling-type fluidized bed combustor and CO, NOx, SOx and HCl concentrations in the flue gas from the combustor were detected by a continuos measurement system. It is found that CO concentration in the flue gas is greatly increased by increasing the RDF feed rate, and CO concentration in the flue gas is greatly decreased by increasing the air ratio because the volatile matters rate is extremely great in combustion of RDF. It is also significantly affected by the secondary air injection and the air distribution ratio from the distributor. HCI concentration in the flue gas is effectively controlled by the calcium compound contained in RDF. HCI concentration is maintained to be less than 60 ppm when the bed temperature is 800 degrees C, and the NCI removal ratio by the calcium component is higher than 70% even though under the higher bed temperature than 900 degrees C. NOx concentration was among 50 similar to 150 ppm and SO, concentration is less than 0.5 ppm.