Composite hollow fiber membranes were prepared by a dry-jet wet spinning process using a double layer spinneret. These membranes were composed of a thin and dense outer-layer of poly(ethylene oxide)-containing polyimide and a sponge-like inner layer of other polyimide. The outer layer was responsible for the separation and fabricated as thin as 1 mu m. The permeation flux of CO2, R-CO2, and the CO2/N-2 selectivity decreased 40% and 10-20%, respectively, in a month after the membrane preparation. The steady performance was still high; for example, R-CO2=69x10(-6)cm(3) (STP)/(cm(2) s cm Hg) and the selectivity of 33 at 323 K.