In this study, a new type DDR zeolite membrane was prepared and its gas permeation and separation mechanisms were studied. Gas permeations of single gases and CO2/CH4 mixtures were measured, and the separation performance of the DDR zeolite membrane was compared with those of other membranes. Measurement of the single gas permeance of He, H-2, CO2, O-2, N-2, and CH4 indicated that the permeation mechanism of CO2 was mainly caused by its adsorption affinity on micropore of the DDR, while that of CH4 was caused by the molecular sieving effect of the 8 ring windows of the DDR zeolite. The maximum CO2/CH4 ideal selectivity at 298 K with the constant pressure method and the sweep gas method were respectively 336 and 170 at the feed pressure of 0.2 MPa and the permeate pressure of 0.1 MPa (atmospheric pressure). Single gas fluxes of CO2 and CH4 and separation factor of equiniolar CO2/CH4 mixtures were compared at the same partial pressure. Over the whole pressure range, the CO2 flux of single gas measured by the sweep gas method was higher than that of the mixtures, whereas the CH4 flux of single gas showed very little change. The separation factor of CO2/CH4 mixtures measured by the constant pressure method and the sweep method had a maximum value of 106 at feed pressure of 0.6 MPa, and a maximum value of 200 at atmospheric pressure. In compassion with the new type of DDR zeolite membrane has higher CO2/CH4 separation factor and CO2 permeance. We concluded that the DDR zeolite membrane was suitable for CO2/CH4 separation.