This study examined the selective removal of gaseous mercury contained in combustion flue gas by potassium iodide (KI) loaded on activated carbon fibers (ACF). Activated carbon, such as ACF, although a useful mercury sorbent, shows poor performance in the direct treatment of high-temperature flue-gases because it removes mercury only by physical adsorption. KI can remove mercury at high temperatures via a gas-solid reaction between mercury and adsorbents, and it has been confirmed experimentally that it shows high mercury removal performance in the temperature range of 100-200 °C. On the other hand, KI in the absence of a porous support with a high surface area has low mercury-adsorption removal efficiency. Hence, a high surface area support is needed for adsorption removal. In the present study, mercury contained in combustion exhaust gas could be removed efficiently using KI as an adsorption activity enhancer on an activated carbon fiber (ACF), which provided a high surface area.