In order to find the factors and their effects for the Ca-based absorbent for CO2-capture, the experimental method was used to research the limestone in the calcination/carbonation fixed bed process. Then measured the specific surface and specific pore volume respectively by the method of COULTER_SA_3100 nitrogen absorption specific surface and the method of BET and BJH through pore size analyzer. The result has showed that the microstructure of absorber and conversion ratio of carbonation X was affected by the operating parameters including calcination temperature (Tcal), CO2 concentration in calcination atmosphere, variable cyclic number N and carbonation temperature (Tcar). In this experiment, X reached its maximum when Tcal was 850°C, with the calcination temperature continued to rise, X reduced gradually. The increase of the concentration of CO2 will strengthen the role of sintering and reduce X in the calcination atmosphere. With the increase of the cyclic number N, sintering effect made the micro-structure of absorbent change, so that X decreased. Tcar close to the limit temperature was appropriate. In the limited temperature range, with the increase of N, conversion ratio of carbonation X declined slowly.