A key concern for application of fixed carrier membranes in CO2 capture is the effects of a trace amount of SO2 present in the flue gas. To eliminate this concern, the effects of SO2 in the feed gas on CO2/N-2 permeance and selectivity of fixed carrier membranes were investigated by combining experimental and modeling study. The experimental results reveal that the separation performance of the membrane slightly decreases with increasing SO2 concentration in the feed gas due to the competitive sorption and competitive reaction caused by SO2. The decrease in separation performance is tolerable at even 5000 ppm of SO2 present in the feed gas. The facilitated transport model was modified by considering the competitive reaction to investigate the transport and interactions of CO2 and SO2. The modeling results suggest that the SO2 partial pressure at the membrane surface is much lower than that in the bulk feed gas due to the serious concentration polarization of SO2 under the mixed gas condition, and the decrease in CO2 permeance is mainly attributed to the competitive reaction.