To improve the CO2 separation performance of a poly(amidoamine) (PAMAM) dendrimer composite membrane, the addition of hyaluronic acid (HA) in a chitosan (CTS) gutter layer and the application of a novel hydroxyl PAMAM dendrimer for CO2 selective material are proposed. The addition of HA in the coating solution for CTS gutter layer fori-nation increased the swelling degree of the corresponding CTS-HA film and led to an increased CO2 permeance of the resulting composite membrane, and a decrease in the CO2/N-2 separation factor. A PAMAM dendrimer composite membrane with CTS-HA(20) gutter layer, which was prepared with a coating solution of 20 wt.% HA solid content, showed a high permeance of 10.0 x 10(-10) m(3) (STP) m(-2) s(-1) Pa-1 while maintaining a high CO2 separation factor of 130. The HA addition increased the PAMAM dendrimer content in the gutter layer. A composite membrane prepared with a novel hydroxyl PAMAM dendrimer in the CTS-HA(20) gutter layer exhibited an excellent CO2/N-2, selectivity of 1100 and CO2 permeance of 8.8 x 10(-10) m(3) (STP) m(-2) s(-1) Pa-1.