A uniform nanoplate-like MgO-based sorbents were prepared with eitelite and hydromagnesite intergrowing each other, and their CO2 capture capacity was evaluated for fast CO2 absorption in the thermal swing absorption process, with model wet industrial flue gas at a CO2 concentration of 14.5 vol %, at ambient pressure. Fast absorption and desorption rate, acceptable dynamic absorption capacity, and good cyclic stability (9 wt % after recycling 100 times) have been obtained. Some theoretical work has been carried out and found eitelite was the only origin of the active MgO species for fast CO2 uptake in TSA process. Nitrate was also demonstrated to have some promotive effect in CO2 fast absorption on the active MgO species. The effectiveness of eitelite was close related to its special crystal structure, i.e., after calcination, the special layer assembling with the proximity of Na+ and O(2- )at a molecular level probably contributed to the fast absorption. Meanwhile, the void space caused by decarbonization of hydromagnesite may also facilitate the absorption and diffusion of CO2 Therefore, this sorbent has been demonstrated to be a potential absorbent for postcombustion CO2 capture from fossil-fuel-fired power plant.