A magnesium based precursor and a binder were used to prepare a magnesium based sorbent by wet mixing method after the process of calcination and hydration. The effects of temperature and pressure on the adsorption properties of the sorbents were investigated. Physicochemical properties of the sorbents were characterized by XRD, SEM and BET. It was indicated that the active component of the hydrous sorbent was Mg(OH)2, whose breakthrough capacity of CO2 reached 3.93 mmol/g under the condition of 300 ℃ and 2 MPa. Antigorite formed in the process of hydration reduced the utilization efficiency of Mg. Block product layer formed on the surface of the adsorbent in the adsorption process restricted the internal diffusion of CO2.The sorbent could perform 18 stable cycles of sorption regeneration under moderate temperature and pressured condition, which was suitable for CO2 capture in IGCC.