Fly ash based adsorbent is dipping modified by NaCl or NaBr solution and the purpose is to improve their oxidation capability. Adsorption experiments of vapor-phase elemental mercury are performed in a laboratory-scale fixed-bed reactor. Physical properties of the adsorbent before and after modification are measured and the influences of the solution concentration and flue gas temperature on mercury oxidation rate are studied. The results show that when NaBr solution concentration is 5%, the mercury oxidation rate can reach 79.43%. The saturation adsorption quantity of absorbent 5%-NaBr is 1 700 ng/g and the service life is about 480 hours. Flue gas temperature played an important role in mercury oxidation and the best temperature ranged from 100 to 200 ℃.