A mathematical model has been developed to predict the performance of a continuous bubbling-fluidized-bed hot-gas desulfurization system in the integrated gasification combined cycle. For both the bubbling-fluidized-bed desulfurizer and the bubbling-fluidized-bed regenerator, the model combines the particle residence time with the kinetic rate in each reactor. The flow pattern of the solid phase was assumed to be well-mixed, and the flow pattern of the gas phase was assumed to be plug flow. The model has been applied to Korea Institute of Energy Research's laboratory-scale fluidized-bed process. The present model provides a reasonable fit in predicting the experimental result that the outlet concentration of H2S increased nearly proportionally to the inlet concentration of H2S in the desulfurizer. The sulfur concentration in both the desulfurizer and the regenerator was predicted to increase exponentially as the inlet concentration of H2S increased in the desulfurizer. The outlet concentration of H2S was predicted to decrease exponentially in the desulfurizer as the static bed height increased in both the desulfurizer and the regenerator. The outlet concentration of H2S was predicted to increase exponentially in the desulfurizer as the gas velocity increased in both the desulfurizer and the regenerator.