In this work, limestone, aluminum nitrate hydrate, and glycerol water solution by combustion synthesis method were proposed to prepare a synthetic CaO/Ca.sub.3Al.sub.2O.sub.6 sorbent for CO.sub.2 capture in calcium looping cycles. The effects of the mass ratio of CaO to Al.sub.2O.sub.3, cycle number, carbonation conditions, and calcination conditions on the CO.sub.2 uptake by the obtained synthetic sorbent in the repeated carbonation/calcination cycles were studied in a dual fixed-bed reactor and a thermogravimetric analyzer. The optimum mass ratio of CaO to Al.sub.2O.sub.3 was 90:10 in the preparation process of the synthetic sorbent, which exhibited a 0.43 g g.sup.-1 of CO.sub.2 uptake after 50 cycles. The main compositions of the synthetic sorbent contained the mass ratio of CaO:Al.sub.2O.sub.3 = 90:10 were CaO and Ca.sub.3Al.sub.2O.sub.6, and the mass ratio of CaO to Ca.sub.3Al.sub.2O.sub.6 was 74:26. The CO.sub.2 uptake by CaO/Ca.sub.3Al.sub.2O.sub.6 increases rapidly with the carbonation time in previous 5 min and then rises slowly after 5 min. The carbonation time to reach the maximum CO.sub.2 uptake rate of CaO/Ca.sub.3Al.sub.2O.sub.6 was much sooner than that of CaO derived from limestone in each cycle. The optimum carbonation temperature window of CaO/Ca.sub.3Al.sub.2O.sub.6 was 650-700 °C. CaO/Ca.sub.3Al.sub.2O.sub.6 sorbent possessed obviously higher sintering resistance than CaO under the more severe calcination conditions in the cycles. The high CO.sub.2 uptake capacity of CaO/Ca.sub.3Al.sub.2O.sub.6 was attributed to its stable porous structure in the multiple carbonation/calcination cycles.