The MSW has been recognized as one of the promising alternative energy resource. Recently dioxin emission has been social concern and the serious regulation less than 0.1ng/m3 was determined for newly built incinerator. To overcome the serious problems of pollutants such as dioxin, NOx, CO and dust in the MSW incinerator, densified RDF(refuse derived fuel) which is classified RDF-5 by ASTM standard is an attractive technology to utilize MSW as the energy resources. Since RDF utilization technologies have significant advantages in storage, transportation and constant heating value. Moreover, the calcium component added in RDF has the capacity to control HCl emission level in flue gas and then higher energy efficiency is expected. The RDF was produced from municipal solid wastes including papers, woods, plastics and clothes for this experiment. In this work, since the most combustible component of RDF is volatilized by pyrolysis, a RDF combustor should be designed to achieve very good mixing and high reaction efficiency of the gas flow field. In order to design the multi-hearth type RDF combustors having capacity of 60kg/hr, computational fluid dynamics was employed to calculate the flow and reaction profiles along with combustion experiments. Through this method imposed a limitation in accuracy, it was applicable to investigate the flow performance governed by the secondary air jets. Using the simulation results, the RDF combustor design including the nozzle arrangement of the secondary air and the shape of the secondary combustion chamber was improved to minimize a dead volume of mixing within the furnace, which resulted in longer residence time and efficient mixing. The results of combustion experiment of RDF showed that the concentrations of CO, NOx, SOx and dust were lower than the regulations of flue gases emitted from the incinerator.