Abstract: The spent fluid catalytic cracking (SFCC) catalysts were activated by an "internal instant vaporization (ⅡV)" method and used in the removal of Hg⁰ from a simulated flue gas in a fixed bed reactor; the effect of various operation parameters such as the SFCC activation conditions, adsorption temperature, and flue gas components on the Hg⁰ removal efficiency was investigated. The results indicate that the SFCC catalyst activated with methanol or ethanol performs adequately in terms of Hg⁰ removal, whilst the calcination temperature also has a great influence on the activation of the SFCC catalyst. O₂ in the flue gas favors the Hg⁰ removal, whilst NO facilitates the oxidation of mercury and displays a positive effect on the mercury removal in the presence of O₂, accompanying with the formation of N-containing active species on the activated SFCC catalyst surface. SO₂ in the flue gas, depending on its concentration, may exert the effect of catalytic adsorption or competitive adsorption on the Hg⁰ removal. Approximately 100% Hg⁰ can be removed in the stream of 6% O₂, 12% CO₂ and 0.06% NO at 120 ℃ by using the activated SFCC catalyst with ethanol as an organic solvent and calcined at 120 ℃, suggesting that the spent FCC catalysts after activation can be a potential adsorbent for the removal of Hg⁰ from the coal-fired flue gas.