In the present study, the thermal and combustion fields of innovative gasification-melting plant for municipal solid waste (MSW) are investigated by computational fluid dynamics. This plant uses exhaust gas after melting process as heat source for gasification of MSW and to control secondary combustion in gasification furnace. The effects of melting exhaust gas injection into gasification furnace are studied varying the flow and thermal conditions. From the results, the injection of high temperature melting exhaust gas can maintain much easily uniform temperature slightly above the gasification bed, which is very helpful to gasification of MSW. Furthermore melting exhaust gas injection generates strong swirl motion in the secondary combustion chamber resulting in increased reaction rate there. These thermal and combustion characteristics are changed by varying the flow and thermal conditions and are scrutinized.