Effects of heat treatment temperature and time on sulfur removal capacity of CuO/γ-Al2O3 sorbent were determined in a thermogravimetric analyzer with a variation of sulfation temperature (300 ℃, 500 ℃). At sulfation temperature of 500 ℃ (bulk sulfation), sulfur removal capacity of CuO/γ-Al2O3 sorbent increases with increasing heat treatment temperature up to 800 ℃ and then decreases. At sulfation temperature of 300 ℃ (surface sulfation), however, sulfur removal capacity of the sorbent remains constant up to 700 ℃ and then slightly decreases. This is because bulk sulfation advances by SO3 gas decomposed from the CuSO4, whereas surface sulfation goes on by surface transfer of SO2 via catalytic function of CuO. Sulfur removal capacity of sorbent heated at 800 ℃ shows a maximum value at the heat treatment time of 12 hr and then decreases with increasing heat treatment time. This is because redispersion of Cu ions is dominant at initial step and then formation of CuAl2O4 increases with increasing heat treatment time by the movement of impregnated copper ions from octahedral (Oh) to tetrahedral (Td) site. Bulk sulfation does not occur in CuAl2O4 due to the strong bonding of SO2 with CuO/γ-Al2O3 and the existence of CuAl2O4 has been confirmed using diffuse reflectance spectra (DRS) and x-ray diffractometer (XRD).