The carbonation reaction characteristics of potassium-based sorbent was investigated with thermogravimetric apparatus（TGA），X-ray diffraction（XRD），scanning electron microscopy analysis（SEM）and N2 adsorption method.The results showed that the carbonation rate of analytical reagent（AR）K2CO3 was rather slow with its composition of K2CO3·1.5H2O.The carbonation rate of the K2CO3 sample without crystal water was also slow，because K2CO3 could react quickly with H2O from atmosphere to produce K2CO3·1.5H2O.However，the conversion rate of the sample reached 85% within 20 minutes，when K2CO3 was provided by decomposition of KHCO3.The sample still kept high activity after several cycles.The different reaction behavior of these samples were analyzed from the microscopic view.And the reaction mechanisms of these samples were discussed.Also the empirical equations of the reaction rates and the kinetic parameter were obtained by the thermal analysis method.The present work has provided the data base for the technology of dry potassium-based sorbent capturing of CO2.