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The capture of CO2 through the use of a CaO-based adsorbent plays an important role in the efficient separation of high temperature CO2 from flue gas and sorption-enhanced hydron production processes [1-3].However,the CaO-based sorbents suffer from the rapid decay of CO2 sorption capacity during multiple carbonation-calcination reaction cycles due to the sintering of CaO or CaCO3 in the regeneration process [4-5].Adding an inert material to improve the resistance of CaO or CaCO3 to sintering was considered as a promising method [6].In this research,MgO was served as an “inert” material in the sense that it did not adsorb CO2,nano CaCO3 coated with MgO as a CO2 adsorbent was prepared by four methods of homogeneous precipitation,simple mixing,sol-gel and adsorption phase reactive technique respectively.The effects of different preparation methods on the cyclic carbonation-calcination reaction performance of the nano CaO-based adsorbent were investigated in this study.The results showed that the nano CaO-based adsorbent coated with MgO prepared by adsorption phase reactive technique method demonstrates the best durability which after 30 carbonation(T=600°C)-calcination(T=750°C) reaction cycles.Its decay ratio of sorption capacity is as low as 20% while the others’ are more than 60%.The effect of different MgO ratio in adsorbent was further investigated while the adsorption phase reactive technique method was used to synthesize the sorbent.The sorbent with a 12% weight ratio of MgO showed a good value of sorption capacity of 3.0 mol/kg after 30 carbonation-calcination reaction cycles and a good durability.The reason is that adsorption phase reactive technique uses the easily controlled adsorption phase as a microreactor to produce MgO to coat on the surface of nano CaCO3 so that finely dispersed inert material and adsorbent was formed which leading to a good stability.