A CO2 capture process for an integrated gasification combined cycle (IGCC) power plant using the calcium looping cycle was proposed. The CO2 capture process using natural and modified limestone was simulated and investigated with the software package Aspen Plus. It incorporated a fresh feed of sorbent to compensate for the decay in CO2 capture activity during long-term cycles. The sorbent flow ratios have significant effect on the CO2 capture efficiency and net efficiency of the CO2 capture system. The IGCC power plant, using the modified limestone, exhibits higher CO2 capture efficiency than that using the natural limetone at the same sorbent flow ratios. The system net efficiency using the natural and modified limestones achieves 41.7% and 43.1%, respectively, at the CO2 capture efficiency of 90% without the effect of sulfation.