In this work, a novel copolyimide (CPI) of 4,4'-oxydiphthalic anhydride-2,4,6-trimethy1-1,3-phenylenediamine/2,6-diaminotoluene was synthesized and its defect-free asymmetric hollow fiber membrane (HFM) was fabricated successfully through a dry wet spinning method with a 33.3 wt % CPI concentration in dope. When tested at 25.0 degrees C and 0.30 MPa, its CO2 permeance was 39 GPU with ideal selectivities of 44.3 over N-2 and 47.0 over CH4. A plasticization test proved that this CPI HFM could be reliably operated with CO2 partial pressure no higher than 2.25 MPa. The highest testing pressure in this work was 6.6 MPa with a gas mixture of CO2/N-2 (50%/50%), and the fibers did not show any mechanical collapse. Continued tests with the same gas mixture showed that CO2 percentage in permeate could be enriched to 93.3-95.1% by a test pressure increase from 0.5 to 4.5 MPa at room temperature. When tested with a feed gas of CO2/CH4 (10%/90%) mixture, CO2 percentage in permeate could reach 59.9-72.7% under similar conditions. An operation temperature increase obviously facilitated gas mixture permeation while the separation performance degraded. At the end, influence of released gas flow rate was investigated with both gas mixtures. It was clearly seen that release flow rate increase was beneficial for gas permeation in HFM, and as a result, higher CO2 concentration in permeate could be seen, while at the same time product quality of released gas was inevitably changed in an undesired way. In conclusion, the prepared CPI HFM shows promising application potential in the field of CO2 separation and capture from natural gas.