A systematic study of catalytic oxidation of sulfur dioxide in a fixed bed reactor operated in flow reversal mode was made. A heterogeneous transient model of the reactor was developed. The global rate equations and the heat transfer parameter correlation were obtained, based on a series of previous experiments. The experiments of unsteady-state oxidation of low concentration SO2 were conducted in a bench-scale fixed bed reactor, packed with a domestic commercial catalyst. The model can successfully predict the transient concentration and temperature profiles when a correction factor is introduced to the global rate equations.