RITE is carrying out a research project to develop membranes for carbon dioxide separation. In the project, we study Cardo type polyimides. Cardo polyimides show good CO2/N-2 separation foctor. We developed new Cardo polyimide which has higher permselectivity, by introduction of a CO2 affinitive functional group. Furthermore we developed wet-spinning method of the new Cardo polyimide hollow fiber, which has sponge-type support structure and inner defectless skin layer. The fiber has both good permselectivity and practical mechanical strength. Since this spring, bench scale test of CO2 separations by this hollow fiber was started.