The dynamic adsorption isotherms of CO2-EGR were measured by using a Intelligent Gravimetric Analysis system.In the beginning stage of CO2 injection, all the injected CO2 enters into the adsorbent and the mole fraction of CH4 (yCH4) keeps 1.0. The CH4 recovery factor (RCH4) increases. The during of this stage (tcd) depends on the selectivity of CO2 over CH4 ( SCO2/CH4). A adsorbent with large SCO2/CH4 has long tCD. When SCO2/CH4 is greater than 1.0, CO2 reduces the fraction of CH4 in the adsorbed phase (xCH4) and more CH4 is driven out. In the second stage,the injected CO2 competes with CH4 for adsorption. The cumulative RCH4 of this stage is much larger than that of the initial stage. However, yCH4 decrease sharply. pCH4 in the whole CO2 injection is always larger than that before CO2 injection, suggesting CH4 desorption results from the displacement by CO2 rather than from pressure depletion.