The gas transport performance through the polydimethylsiloxane (PDMS)/polysulfone (PS) composite hollow fiber membranes is investigated. A resistances-in-series model based on the Henis-Tripodi's model and the theory of the boundary layer for gas separation in composite membranes is presented, in which the resistance of the boundary layer and the resistance of membrane have been taken into account. This model can be used to predict the membrane performance for refinery dry gas separation, which is replaced by the mixed gas of 40% H-2/10% N-2/50% CH4 (volume fraction) in the experiment. Then the influences of feed flow rate, feed pressure, and the partial pressure of hydrogen in permeate gas on gas permeance and selectivity of membranes have been considered and analyzed. Although the present work focused on PDMS/PS composite membranes, this model also can be applied to the other so-called "resistance model" type membranes. (C) 2003 Published by Elsevier B.V.