The aims of this work were verifying the roles of various promoters in absorption and regeneration. In particular, we focus our attention on the oxidation properties of Ce, Co, and Fe and regeneration property of Fe of the MgO-based sorbents. The MgO-based SO2 sorbents promoted with Ce, Co, Fe, and Cu were developed for use in RFCC and FCC units. Their ability for SO2 absorption as well as regeneration was investigated in a fixed-bed reactor under RFCC and FCC reaction conditions. The promoters played an important role in transforming SO2 into SO3, which could be easily absorbed into MgO. Their oxidation ability increased in the following order Fe < Co < Ce. In addition, their reuse through the regeneration of sorbents with hydrogen in a FCC unit depended on these promoters. In particular, the MgO sorbent which was promoted simultaneously with Ce and Fe showed excellent characteristics in SO removal and regeneration in that this material satisfies the requirements of a large amount Of SO2 absorption (ads. sulfur g/g sorbent) along with fast and complete regeneration under mild condition (1 atm, 530 degrees C).