This study examined the effects of additives to improve the COS absorption capacity of Cu-Al-based sorbents for the integrated gasification fuel cell (IGFC) process. To absorb a small amount of COS, an Al-based precursor was added to the precursor solution for Cu-Al-based sorbents because a high surface area absorber was required. Various transition metals (Zn, Fe, Mn) were used as additives to improve the stability of the Cu-Al-based absorbent. The changes in surface properties and sulfur absorption capacity of the Cu-Al-based absorbent were investigated according to the composition of transition metals. As a result of the sulfur absorption test, the difference in the sulfur absorption capacity of the Cu-based sorbents was confirmed depending on the type of additive, and changes in their surface area. Moreover, the pore characteristics were observed by the nitrogen adsorption method. Sorbents with high surface areas generally have high sulfur capacity, but the additive component has a strong effect. These results can be explained by the transition metal additive binding to Cu to form a composite metal oxide. Furthermore, manganese was found to be suitable for improving the stability and surface area of the copper-based absorbent.