Abstract: A new polymeric membrane material-polyvinylamine (PVAm), which contains amino-groups facilitating the transport of CO 2 in the membrane, has been developed. A composite membrane used for CO 2 separation was made up by covering a PS basis membrane with the polyvinylamine. Sorption of CO 2 on the PVAm-PS composite membrane and the PS basis membrane was measured by using the volumetric method. The results show that the composite membrane has very high CO 2 sorption capacity, and this sorption capacity arises mainly from the PVAm layer. Temperature has much impact on the sorption, the sorption capacity drops sharply when temperature increases. The sorption mechanism is analyzed. It is deduced that there are physical and chemical interaction simultaneously between the composite membrane and CO 2. The membrane has no obvious sorption for CH 4, N 2 and H 2.