In this study, we investigated the effects of one-step chemical vapor deposition (CVD) of propylene on the pore structures and gas separation performances of carbon hollow fiber membranes derived from sulfonated poly (phenylene oxide) (SPPO). The CVD is performed by feeding a 5-100% of propylene gas at the carbonization peak temperature. The obtained CVD carbon membranes had higher carbon concentrations and were hydrophobic. Their water permeances were considerably lower than those of uncoated membranes in pervaporation experiments. The gas permeances of the CVD membranes also decreased but the ideal selectivities greatly improved, especially for H-2/CH4 from 130 to 1625 with the membrane prepared by pyrolysis at 650 degrees C for 60 min in combination with CVD of 100% propylene for 5 mM. We found that the gas separation performance could be easily controlled by changing the propylene volume fraction and CVD time. The highest H-2/CH4 selectivity of 29,940 was obtained for a membrane pyrolyzed at 700 degrees C for 20 min with CVD using 10% propylene for 20 min.