In this paper, a three-dimensional numerical model has been developed to study the gaseous pollutant emissions during the circulating fluidized-bed (CFB) combustion of combustible solid waste. On the basis of the Eulerian-Eulerian approach, the gas phase is modeled with a k-epsilon turbulent model and the particle phase is modeled with a kinetic theory of granular flow. The hydrodynamics, heat and mass transfer, and chemical reactions are simultaneously taken into account. Reactions during combustion consist of waste devolatilization, volatile combustion, char combustion, SO2 formation and recapture by calcium oxide, NO and N2O formation, and diminution by heterogeneous and homogeneous reactions. The model has been applied to the CFB riser with a height of 1.8 m and a diameter of 0.125 m at atmosphere. The influences of an excess air ratio on the emissions of SO2, NO, and N2O are studied. The model predicts a growth in the SO2 emission when excess air increases. The emissions of NO and N2O also gradually increase with the increasing excess air ratio. Meanwhile, the CO and CH4 concentrations show a decreasing tendency. The distribution of the bed voidage, flow pattern development, profiles of gas compositions, and related reaction rates inside the riser are also discussed.