Blend membranes have attracted great attention because they can combine the advantages of different polymers. To investigate the effect of amphiphilic polymer on the separation performance of blend membranes, a series of blend membranes were designed and fabricated by blending an amphiphilic polymer of poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) into poly(ether-block-amide) (Pebax) polymer for CO2 separation. For the as-prepared Pebax/PEDOT:PSS blend membranes, the interconnected CO2-philic networks were constructed by hydrophilic anionic chains of PSS- for accelerating CO2 transport. Meanwhile, non-CO2-philic networks were constructed by the hydrophobic cationic chains of PEDOT+, which distributed around the PSS- chains to provide low friction diffusion for CO2. Therefore, the amphiphilic polymer of PEDOT:PSS was an excellent material for improving CO2 separation performance of blend membranes. The results showed that the Pebax/PEDOT:PSS blend membranes were endowed with excellent CO2 separation performance. Pebax/PEDOT:PSS blend membrane demonstrated the optimal separation performance with a CO2 permeability of 440.2±3.3 Barrer and a CO2/CH4 separation factor of 28±0.6. This study indicates that introducing the amphiphilic polymer into the blend membranes is an efficient strategy for gas separation.