A series of polyurethane-polystyrene (PU-PS) interpenetrating polymer networks(IPN), semi-IPNs(only the PU component is crosslinked), and linear blend membranes were prepared while synthesis temperature and composition were varied. Due to the homogeneity increase of PU and PS, the permeability coefficient decreased and the separation factor increased for preparations made at the lower temperature. The permeability coefficient increased in the sequence IPN, semi-IPN, and linear blends. Annealing effect on the permeation characteristics was dependent on the cross-linked nature of the membrane (IPN<semi-IPN<linear blends). The change of homogeneity, which was modulated by the change of composition, cross-linked state, synthesis temperature, and annealing temperature. Could play an important role to control the gas transport characteristics.