The properties of sequential CO2/SO2 capture using CaO-based sorbent reactivated by steam were studied experimentally with two tube furnaces(TF)，a steam generator and a thermogravimetric analyzer(TGA).The pore structures of samples at different stages of experiment were investigated by N2 adsorption-desorption.The results showed that the residual carbonation activity for the sorbent after 40 CO2 looping cycles under dry condition was only 18%，while the sulfation activity for that sample was 44%，only 4% lower than the original sample，indicating that the spent sorbent in CO2 capture was still active in SO2 retention.The highly cycled sorbent could be reactivated by steam at 100℃ under atmospheric pressure，and the carbonation activity could be restored to about 68% which decayed in the next CO2 looping cycles in the same way as the fresh sample.The average conversion of the sorbent during 20 cycles could be kept at above 65% when one steam reactivation is conducted after every two CO2 looping cycles.It was the loss of surface area and pore volume that caused the decay of sorbent activity，while the sulfation conversion was not proportional to surface area or pore volume.Although the original sample had the best pore structure， the steam reactivated sorbent got the highest sulfation conversion of 80%，much higher than the original sample.From SEM analysis，the improvement resulted from the fracture of sorbent during hydration and dehydration，which provided more particle outer surface where reaction product could grow freely.The product growing space had a greater influence on sulfation than on carbonation due to greater molar volume of CaSO4 than CaCO3，thus sulfation conversion was higher than carbonation conversion for reactivated sorbent and highly cycled sorbent with more macropores.Despite particle attrition，it was practical to use CaO-based sorbent with steam reactivation for capturing CO2 and SO2 sequentially.