Carbon membranes for gas separation were prepared from the polymer blend consisting of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and polyvinylpyrrolidone (PVP) as the thermally stable and labile polymer, respectively. The PPO/PVP derived carbon membranes with lower PVP concentrations than 0.6 wt% showed decreased gas permeances and increased permselectivity due to decrease in the pore properties (pore volume and surface area). Meanwhile, gas permeance increased for the carbon membranes prepared with higher PVP concentrations than 0.6 wt% due to the enhanced diffusional pathways for the gas transport through carbon membranes especially in the domain of the thermally labile polymer. It is considered that the introduction of the thermally labile polymer leads to control the pore structure through the permeation results for the carbon membrane derived from the polymer blend.