Numerical simulation was conducted by coupled analysis of DEM (Discrete Element Method) and CFD (Computational Fluid Dynamics) for a full-scale rotary combustor for municipal solid waste. The numerical analysis was conducted under general operating conditions and under conditions where the heating value of waste was reduced. As a result, the residence time of waste in the incinerator was almost the same as the past measurement results. However, it was suggested that the char combustion rate of the particles in this simulation was significantly different from the actual phenomenon and should be improved. When the heating value of the waste was reduced, the expected results were obtained, such as an increase in the concentration of H2O in flue gas due to an increase in moisture of the waste, and an increase in O2 concentration due to an increase in an excess air ratio.