Abstract: In this paper, poly (amide-6-b-ethylene oxide) (PEBA1657) copolymer was used to prepare multilayer polyetherimide (PEI)/ polydimethylsiloxane (PDMS)/PEBA1657/PDMS composite membranes by dip-coating method. Permeation behaviors of ethylene, ethane, propylene, propane, n-butane, methane and nitrogen through the multilayer composite membranes were investigated over a range of operating temperatures and pressures. The permeances of light hydrocarbons through PEI/PDMS/PEBA1657/PDMS composite membranes increase with their increasing condensability, and the olefins are more permeable than their corresponding paraffins. For light hydrocarbons, the gas permeances increase significantly as temperature increasing. And their permeances increase with the increase of transmembrane pressure difference due to plasticization effect, while their apparent activation energies for permeation decrease.