Gas separation membrane systems have been received a lot of attention, and various membrane materials have been synthesized and investigated for gas separation applications in the last two decades. This is due to the fact that membrane separation processes may offer more capital and energy efficiency when compared to the conventional separation processes such as cryogenic distillation, adsorption and pressure swing adsorption in some applications. Among the polymers for gas separation membranes, aromatic polyimides are one of the most attractive and promising materials due to their high thermal stability, glass transition temperature and a relatively low dielectlic constant. Various polyimides have become increasingly important in a variety of technological applications, such as distillation, gas separation, and dialysis and so on. In this study, we synthesized novel polyimides with high gas permeability and selectivity for application gas separation. 2,2-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) and two kinds of diamines with high permeability and solubility were used to prepare the novel polyimide. 2,3,5,6-Tetramethyl-1,4-phenylenediamine(TMPD) was used to improve gas permeability and various kinds of diamines were used to improve the gas selectivity respectively. The polyimide copolymers were synthesized by commercial chemical imidization method and their average molecular weights were over 100,000g/mol. The glass transition temperature (Tg) and the thermal degradation temperature were characterized using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The synthesized copolymers showed high Tg over 300°C and high thermal degradation temperature over 500°C. The gas permeation properties were measured by time-lag equipment. Although general polyimides showed very low gas permeability, synthesized polyimide copolymer showed high O2 permeability of 36.21 barrer with high O2/N2 selectivity around 4.1. The hollw fiber membrane containing various additives was prepared by phase inversion method. Their morphologies and gas permeation properties were examined. The hollow fiber membranes were prepared by control of dope extrusion rate and air gap distance. The gas permeance decreased with increasing air gap distance whereas the selectivity increased with increasing air gap distance, resulting from the thin skin layer formation. The CO2/N2 selectivity of hollow fiber membrane was 22.3 at 20cm air gap.