The invention discloses an ytterbium-doped CO2 adsorbent. The ytterbium-doped CO2 adsorbent is composed of ytterbium oxide and calcium oxide in a mass ratio of 1:19 to 1:3, wherein the ytterbium oxide is uniformly distributed in the CO2 adsorbent for improvement of the sintering temperature of the CO2 adsorbent, so the cycle performance of the CO2 adsorbent is improved. The invention also discloses a preparation method for the CO2 adsorbent. The CO2 adsorbent with good high-temperature adsorption performance and cycle performance can be prepared by using the preparation method in the invention; the prepared CO2 adsorbent has adsorption capacity as high as 0.70 g of CO2 per g of the adsorbent and can maintain the adsorption capacity of 0.50 g of CO2 per g of the adsorbent after 15 adsorption/desorption cycles; and the preparation method for the adsorbent is simple and low in cost, and has low requirements on the parameters of preparation process and good industrial application prospects.