A biocompatible, nontoxic, and nonvolatile compound, α-D-glucose pentaacetate (GPA), was impregnated in supported ionic liquid membranes (SILMs) and used for the selective separation of CO₂ and SO₂. It was found that GPA could cooperate with [Bmim][BF₄] to influence the permeability of CO₂ and enhance the CO₂/N₂ selectivity. Further permeation experiments demonstrated that the addition of GPA could reduce the permeability of N₂ in the SILMs and thereby improve the CO₂/N₂ and SO₂/N₂ selectivities. The highest CO₂/N₂ selectivity obtained in the paper is 79 ± 0.9 for dry gas and 86 ± 1.6 for humidified gas, and the highest SO₂/N₂ selectivity is 686 ± 19.8 for dry gas. This environmentally benign separation process with high gas permeability and good selectivity may be expected to have a potential application for the separation of CO₂ and SO₂ from a flue gas stream.